the Geological Survey of Canada, the specific name of Canadensis, as originally bestowed on this trilobite by the author, has been retained. Barrande, in the work just cited, alludes to another American trilobite in the possession of M. de Verneuil, but unnamed and unfigured, with which our species may very possibly agree: only, the caudal shield of this specimen would appear to possess no lateral segmentation, and to have a scarcely defined axis, as M. Barrande refers it to the platycephalus or gigas type.' * His statement respecting it is as follows:-" Nous avons vu récemment, dans la belle collection de notre ami M. de Verneuil un Asaphus des Etats-Unis, qui, portant à l'angle génal une pointe longue et grêle, constitue une espèce très distincte d'As. (Is.) gigas. Malheureusement, nous ne savons quel est le nom spécifique qui lui a été donné par les savans Americains. Ce trilobite se rangerait dans le group de A. gigas, d'après les souvenirs qui nous restent de sa conformation."

§ 2. Description of Asaphus Canadensis. This description is based on what is probably the long or male form.

General outline, a broad oval. Vertical to transverse diameter, nearly as 3:2. Relative lengths of head-shield, thorax and pygidium, as 1 : 0.88: 1.1.

Head-shield obtusely pointed anteriorly, much as in Asaphus platycephalus. Genal angles terminating in sharply-pointed horns of the Paradoxides type, extending downwards to about the middle of the body.† Facial suture, as shewn in the figure; the branches uniting in an obtuse but clearly defined angle above the glabella, nearly at the extreme anterior margin of the head-shield, and terminating at the lower margin, about midway between the glabella and the genal angles. Glabella, feebly raised, broad, and generally conformable at its upper part to the outline of the facial suture. At its base, there occurs a slight but evident neck-furrow. There are no furrows on the glabella itself. Length of glabella to length of head-shield, as 0.8: 1.0. Eyes, moderately raised, and delicately reticulated; although, in most specimens they are more or less destroyed. Breadth between the eyes, to extreme breadth of head-shield across them, as 5:11. Whole surface of the head-shield covered with fine punctures, except at the striated limb.

Thorax, with eight segments. Axis well defined; narrow, somewhat broader in the middle than at the ends. Mean breadth of axis, to

* It is perhaps the Asaphus Iowensis of Dale Owen.

+ In most specimens, as in the figure, the horns extend to the bottom of the fourth thoracic segment; but in a small specimen obtained quite recently from Whitby, and kindly submitted to us by Mr. J. F. Smith of Toronto, they reach to about the middle of the sixth pleura. In our figure they do not make a sufficiently sharp angle with the lower border of the head-shield.

breadth of each side-lobe, as 5 to 6. Pleura, terminating in slight points, and curving slightly downwards*; furrowed to about half their length from the axis, and then crossed obliquely by a curvilinear ridge. A second, but slighter, furrow runs along the lower edge, and two short deep furrows shaped together like the letter V placed upon its side with the point inwards, separate each pleura from its axis-segment. Beyond the ridge the points are delicately striated. Fine punctures occur upon the axis and also on the pleura. On the latter the punctures are larger and farther apart; and when examined through a magnifying glass, they appear to be of a semi-lunar form with the convex side turned inwards. They are likewise more deeply indented

at the convex side.

Pygidium, oval, with striated limb and well developed, tapering axis. This terminates somewhat abruptly before reaching the end of the pygidium. It contains from 12 to 14 segment-markings, and a similar number are present on the side-lobes. All are destitute of secondary furrows. Those on the side-lobes bend downwards near their extremities, and merge into the striated limb. The lower ones are nearly vertical. The whole surface of the pygidium is covered with fine punctures shaped and arranged exactly like the punctures on the surface of the thorax. Asaphus platycephalus, as mentioned by Professor Hall, exhibits in some specimens a delicately punctured surface; but in the present species the punctures appear to be much more striking. Our other new species, A. Halli, is also very visibly punctured; although the punctures, as shown in our figures, are too coarse and too far apart.

The only specimens of Asaphus Canadensis hitherto obtained, have been procured from the Utica Schist (Lower Silurian) of the Townships of Whitby and Nottawasaga, (localities about eighty miles apart), in Canada West. They occur in association with Triarthrus Beckii. In length they appear to vary from about an inch and a half (=38.1 millimetres), to about five inches (=127 millimetres). I have not yet been able to observe the under side, so as to make out the direction of the under sutures, and the form of the hypostoma. An isolated hypostoma, however, found near Whitby, probably belongs to this species. It is badly preserved, but it appears to resemble very closely the hypostoma of A. platycephalus.

*In the horned Asaphidæ, and in nearly all the horned trilobites, the pleura point downwards, whilst in the forms with rounded genal angles, the pleuræ have almost invariably an upward curve, as in the figure of A. Halli, on page 236. When the side-pieces or cheeks of the head-shield are broken off, we may generally determine the nature of the genal angles by this character.

VOL. III.

§3. Specific Differences :-(1.) Asaphus Canadensis differs from A. platycephalus, Stokes (Isotelus gigas, Dekay); A. expansus, Linn; A. Barrandei, de Verneuil; A. læviceps, Dalman; A. (Is.) affinis, McCoy, (including Is. gigas, Is. planus and Is. Powisii of Portlock)— in having, with other opposing characters, the genal angles of the head-shield extended into horns.

(2.) It differs from A. tyrannus, Murchison; A. Powisii, Murchison; and A. ingens, Barrande-in having, with other opposing characters, the branches of the facial suture united above the glabella on the upper surface of the head-shield.

(3.) It differs from A. nobilis, Barrande-in wanting the curved furrows on the axis of the pygidium, as exhibited by that species; and also by the greater number of the segment-markings on the side-lobes of its pygidium, as well as by the general outline of the facial suture, and other characters.

(4.) It differs from A. extenuatus, Waldheim-by the obtuse outline of its cephalic shield, and by other marked characters.

(5.) It differs from A. (Is) laticostatus, Green-the genal angles of which are unknown-by its thorax being nearly of the same length as its head-shield, and by the greater number of segment markings on the side lobes of its pygidium, as well as by other characters.

(6.) It differs from A. ovatus, Portlock, by the presence of segment markings on the side lobes of its pygidium. I am not acquainted with the head-shield of A. ovatus, and I cannot obtain here a copy of Colonel Portlock's Report in which the species is figured.

(7.) It differs from A. angustifrons, Dalman; and A. frontalis, Dalm.; by the greater development of its genal points, Dalman's species being placed by him under his subdivision of "Mutici," comprising the forms with rounded or but slightly pointed genal angles. I am not sufficiently acquainted, however, with these Swedish species to name any other distinguishing characters, and I have no means of procuring here a copy of Dalman's "Palaeden," in which the species are described.

(8.) It differs from A. Iowensis, Dale Owen, by its genal points reaching only to the middle instead of to the end of the thorax; by its facial suture being pointed, instead of curved, above the glabella ; and by the presence of segment-markings on its pygidium.

The head-shields of A. grandis, Sars; A. Fournetti, de Verneuil ; and A. latimarginatus, Hall-are yet unknown.

Finally, apart from the absence of secondary furrows on the pygidium segments, Asaphus Canadensis differs from the generally admitted species of Ogygia, by the following characters:

(1.) From O. Buchii, Brongniart; and O. (?) Portlockii, Salterby the branches of the facial suture being united on the upper part of the head-shield.

(2.) From O. (?) Guettardi, Brongniart; 0. (?) Desmaresti, Brong.; O. (?) Brongniarti, Roualt; and O. (?) Edwardsi, Roualtby the angular junction of the branches of its facial suture above the glabella.

(3.) From O. radians, McCoy-by the large number of the seg ment-markings on the axis of its pygidium, O. radians exhibiting only three. The head-shield of O. radians is unknown, but McCoy refers the species to Ogygia, on account of the short segmental furrows between the larger markings on the side lobes of the pygidium.

II. ON A SECOND NEW SPECIES OF ASAPHUS FROM CANADIAN ROCKS.

The accompanying figure represents a new species of Asaphus, from the Trenton limestone (Lower Silurian), of Peterborough, and other localities in Upper Canada. The same form is believed to occur also in the Utica Schist. General outline, a broad oval; length to breadth, as 3 to 2, or thereabouts; relative lengths of head-shield, thorax, and pygidium, as 1: 0.87 0.87.

Head-shield obtusely pointed anteriorly, and much resembling that of A. platycephalus in its general outline. Limb striated with concentric lines; genal angles rounded; facial suture as shewn in the figure. The branches unite above the glabella in a well-defined angle, almost touching the extreme anterior margin of the head-shield, and they terminate at the lower margin, about midway between the glabella and the genal angles. Where they join this lower margin they make a short curve inwards (see the figure), somewhat as in A. expansus, a peculiarity not exhibited by the facial sutures of A. platycephalus (?) or A. Canadensis. Glabella, feebly raised, and divided into two disinct portions; the lower portion of a semi-oval shape, is defined, as it were, by a prolongation of the body axis. Directly above this, an undulating furrow occurs (as shewn in the figure), strongly marked in