at an earlier period, for among several specimens caught in July, only one was full of young, and that was a younger specimen. The body is dark olive above; sides with alternate silver-gray and rusty bands; fins brown. In younger specimens the longitudinal bands are more yellow, and the fins also yellowish.

RHACOCHILUS, Agass.-In this genus the vertical fins have the same structure as in Embiotoca and the sexes differ in the same manner; but the jaws are very protractile, almost as in our southern Lachuolamus, and the lips very fleshy, the lower lip especially broad, lobed and have their outer margin free from the jaw bone all round, and not attached by a frenum to the chin, as in Embiotoca and Amphistichus. Teeth few and only in front of the jaws, and none on the sides. The body is also more elongated. The young differ widely from those of the preceding genus: their form is more elongated, the caudal remarkably large and long and truncate at its extremity, whilst it is forked in Embiotoca; and the extremities of the dorsal and anal extend beyond the base of the caudal, whilst in Embiotoca they do not even reach it; finally there is no black speck upon either the dorsal or the anal.

Rhacochilus toxotes, Agass.-Color uniform olive above; sides silvery with light longitudinal bands; female darker than male; vertical fins and ventrals dark; male blackish upon opercule and cheeks. Female with mature young in July.

AMPHISTICHUS, Agass.-The spinous rays of the dorsal shorter than the soft rays, but gradually increasing in length, so that the soft portion of the fin does not rise abruptly higher than the spinous portion, though the anterior soft rays are the longest of the fin. Articulated rays of the anal all divided, and not simple in frout as in Embiotoca, nevertheless the fin is separated into an anterior and a posterior portion, by the introduction in the male of a short flat-triangular ray, which produces a deep emargination in the outline of the fin, and in the female by the presence of two or three articulated rays of equal length with the others but much stouter and oftener divided. In the male the anterior rays are swollen as in Embiotoca and Rhacochilus. Papilla of the males very large. Jaws little protractile; with two rows of teeth above and below, lips thin, lower lip not free in the middle. The young have not been observed, the specimens obtained having been caught in January.

Amphistichus argenteus, Agass.-Bluish gray above, sides şilvery with occasional indistinct and irregular transverse bands of olive color. Vertical fins yellowish.

HOLCONOTUS, Agass.-Dorsal long, and lowest behind, its spinous rays being the longest; the anterior and posterior parts of

this fin are not separated by a depression, but its outline descends regularly from the fourth or fifth anterior spinous rays to the posterior extremity. Structure of the aual the same as in Amphistichus but proportionally longer; the sexes differing also in the same manner. Young not known, the fernale obtamed having been caught in January. Jaws very slightly protractile, lower jaw projecting; two rows of teeth in the upper jaw ouly. Lips not fleshy; lower lip free all round.

Holconotus rhodoterus, Agass.-Bluish gray above, silvery upon the sides with rose colored spots in irregular longitudinal lines; vertical fins, especially the caudal, reddish.

I have just been informed (February 25th) that the California Academy of Natural Sciences claims for Dr. W. P. Gibbons the discovery of the viviparous fishes upon which I had established the family Holconoti and the genus Embiotora; but upon what ground I am not informed. This is a question in which I am entirely disinterested, having thus far been only the historian of the discovery and the biographer and godfather of the fishes. Dates and reference to other publications which may have been made in California, will easily settle the question of priority which as far as the discovery of the viviparity of these fishes is concerned, rests between Mr. Jackson and Dr. Gibbons, and not with me. I learn also, from the same quarter, that Dr. Gibbons has dedicated to me a new species of this family and that the Califoruia Academy has inscribed another species to him; but I have not yet seen descriptions of them. Should either of these species coincide with one or the other of those described above, I shall of course adopt, in the more elaborate paper, accompanied with figures, which I am now preparing upon this family, the names first established in accordance with the rules of our science.

The knowledge of this curions family is likely to lead to many other interesting disclosures. Dr. Thom. H. Webb, one of the scientific corps of the Mexican Boundary Line Commission, has sent me under date of Dec. 9th, 1853, the following abstract from his diary, dated San Diego, May 3, 1852: "Capt. Ottinger, of the U. S. Revenue service, caused his seine to be drawn for us to-day. Caught many Tiger and Shovel-nose sharks, two flounders, . . . also a number of small fish, about two or three inches long, each of which contained ten or twelve living young." He adds: "The viviparous progeny I exhibited to the Commissioner and several of the gentlemen of the Commission; and I also kept quite a number of them alive, in a vessel of water, for some days. In the mother they were not, so to speak, indiscriminately huddled together, but methodically arranged, and so placed in relation to each other as to form a compact series, without the loss of interstitial space, in other words, so disposed as to best accommodate the family. On leaving San Diego, I took extra pains to preserve

specimens of this fish, but these special efforts proved an injury," &c. We may therefore confidently look forward for some new type of viviparous fish from San Diego. Mr. Wm. Couper of Toronto, Canada, writes me also that an intelligent young man residing in Buffalo, New York, obtained some fish taken at Black Rock, in which a number of young were found enclosed in a pouch attached to or near the back bone, resembling the parent in form. May this not be some Cyprinodent? I am inclined to believe it, since I have of late ascertained that many of our representatives of that family, if not all, bring forth living young, though these are very small at the time of their birth.

That among our Sharks the Dogfish (Acanthias americanus, St.), is viviparous, has long been known. So is also Mustelus Canis, Mitch. But Mr. Thayer S. Abert, of the U. S. Engineers, informs me that the Stingray of the coast of North Carolina also brings forth living young. This would be, as far as I know, the first example of a viviparous species in the family of Rays.

ART. XXXIX.-Observations on the Development of the "Surinam Toad" (Pipa Americana); by JEFFRIES WYMAN, M.D.

(Presented to the Boston Society of Natural History.)

THE specimens upon which the following observations were made, were obtained by Dr. Francis W. Craigin, U. S. Consul, to whom the Society has been so frequently indebted for his generous and munificent contributions to its cabinet, of zoological collections from South America. The habits of these extraordinary animals during the reproductive season are well known. The eggs are transferred by the male to the back of the female, to which they adhere, and where they are impregnated; their presence excites increased activity in the skin, it thickens, is gradually built up around each egg which it at length nearly encloses in a well-defined pouch; this process of investment has been compared by J. Müller and others to the inclusion of the mammiferous ovum by the deciduous membrane of the uterus. The opening which is left after the pouch is formed, is at length closed up by an operculum, and thus the egg is shut off from all direct communication with the air.

Of the eight specimens which I have examined, two were destitute of eggs in the back, and the skin of these presented a uniform surface throughout covered, as is usual, with conical papillæ. One of them I ascertained by dissection to be a female, the ovaries being well filled with eggs. In the backs of all of the others, ova existed in different stages of development, the number of eggsacs varying in different specimens from forty to one hundred and

fourteen. The structure of the sac may be understood from an inspection of fig. 1, which represents a magnified vertical section through the whole thickness of the skiu: a represents the operculum, b the epidermis, ce dermis or true skin, and d the yelk with its embryo. The sacs are at variable distances from each other, sometimes so closely approximated that the interveuing integument is reduced to the thickness of a piece of paper. The operculum adheres to the circumference of the month, and there is usually found just beneath it a layer of gelatinous matter which is continuous, in some instances at least, around the whole circumference of the egg. The structure of the operculum as seen beneath the microscope was not homogeneous, but seemed to be composed of ill-defined fibres, not unlike those of the white element of areolar tissue, and there were intermixed with them granules of pigment. The interior of the pouch was covered by a layer of pavement epithelium, continuous at the orifice with the cuticle covering the surface of the body; it was easily detached, and its cells were nucleated and contained colored granules. Beneath the skin there exists over the whole back a large cavity, as in Frogs, but unlike the one in them no nerves were seen passing through it, in the region of the spine, to the integuments.

The eggs are quite remarkable when compared with those of other Batrachians for their great size, the yelk alone measuring one-fourth of an inch in diameter. In almost every instance, on removing the operculum, the embryo, however small, was found just beneath it, and thus occupying a position on the yelk which had the nearest proximity to the air.

In the earlier stages, as seen in fig. 2, the head is broad and flat, the cerebral vesicles are easily detected, the lateral portions not having united on the median line; the eyes were prominent

and black; the spinal canal was closed and the ventral lamina were just beginning to extend upon the upper surface of the vitellus; the arms consisted of pyriform processes from anterior portion of the trunk, but the legs consisted of oval masses entirely disconnected with the parts surrounding the vertebral column, and seemed to have an independent centre of growth, and therefore did not bud out from the trunk. In all of the earlier speci

mens three branchial appendages were visible on each side of the head. The general aspect of the embryo, as it lies extended on the surface of the yelk, reminds us of the larval condition of Salamanders and Tritons. The vitelline vessels communicated with the trunk by means of two afferrent vessels on each side of the head, and several efferrent ones on the sides of the trunk.

In a later stage as exhibited in another series of embryos (fig. 3), the external branchiæ had disappeared, the legs (a) now united with the trunk, were terminated by an expanded extremity, the rudiment of a foot; the ventral laminæ as represented by the dotted line extended farther down upon the yelk, but still this last was to a great extent uncovered; the nostrils were visible as round terminal depressions, but it was not ascertained if they communicated with the mouth. A small branchial fissure was detected on each side of the neck, and within this, as was shown by slitting open the mouth and oesophagus, there existed on each side a series of fringed branchial arches.

The most extraordinary feature however of this stage was the peculiar change going on in the yelk mass; the whole of the yelk substance was moulded into a spiral coil, fig. 3, and invested with a thin tunic, and thus converted at once into a spiral intestinal canal, the coils of which extend from the sides of the trunk to the most prominent portion of the yelk, and there changing direction and occupying the axis of the coil the intestine passes back again towards the trunk. The whole yelk-mass is therefore moulded into a spiral intestine.

In the most advanced stages which were examined (figs. 4 and 5) the ventral laminæ had almost entirely included the iutestinal canal as seen in fig. 5; the papillæ and rows of tubercles upon the skin were developed, the intestine had increased in length, and the extremities had become elongated and were provided with well defined toes. The legs were folded against the sides of the body, usually one towards the back and the other towards the abdomen, and the tail which had become proportion