the other members of the genus, has the formula BXY+. The pterylosis is as in the Charadriidæ, but the number of rectrices may be as numerous as fourteen. There is no hallux. In the skull the absence of basipterygoid processes (sometimes indications of them are present, according to GADOW) and the holorhinal character of the nostrils distinguish this family from the Charadriida. The depressions for the supra-orbital glands are well marked. The lacrymal bones are nearly (occasionally quite, though by suture) united with a process of the frontals, and form a canal, through which the gland apparently passes; this is seen in a more exaggerated way in Chionis and in Vanellus (v. description of Chionididae). The post-orbital angle is not distinct from the post-frontal process. There are no occipital foramina, as in Charadriidæ. There are sixteen cervical vertebra, the last three of which have ribs of progressively increasing length; five or six ribs articulate with sternum. Contrary to what is found in the Charadriidæ, the coracoids slightly overlap at their external articulation.

Some of the visceral characters have been already dealt with above in the general description of the Limicolæ.

There is a tendency for the ambiens not to cross the knee; this occurs individually with specimens of several species. The syrinx has not, except as an occasional variation, any intrinsic muscles.

Edicnemus bistriatus has on the anterior wall of the cloaca two hardly elevated ridges, which end by slightly free points, and seem to represent a rudimentary penis.

The surgeon birds and jaçanas of the tropical regions of the Old and New Worlds, with their enormously elongated feet and their somewhat rail-like aspect, are now known to belong to the Limicolæ (and not to the Ralli), of which they may be regarded as forming a distinct family, Parridæ. Their anatomy has been chiefly studied by FORBES.' As with the Thinocorida so with the present family there is a character of the alimentary canal which immediately distin

'Notes on the Anatomy of the Jaçanas,' P. Z. S. 1881, p. 639.

guishes them from all their allies. In this family the cæca are mere passeriform nipples, measuring from 15 to 2 of an inch in length.

The muscular anatomy has already been to some extent treated of in connection with the structure of the entire group of birds of which the present genera form a family. In all of them, Parra, Hydrophasianus, and Metopidius, the muscle formula is complete, i.e. ABXY+. The condition of the deep flexor tendons of the foot is very singular. As FORBES justly pointed out, the peculiarly large size of the hallux (as of all the digits) of the foot in these birds seems to be unreconcilable with the entire absence of a special slip from the conjoined tendon of the long flexors. This fact,' he thinks, 'seems to indicate that the Parrida may have been developed from some form with a more normal-sized foot, and a small hallux which had no special long flexor, the great size of their feet having been developed in accordance with their peculiar habits.'

The syrinx has a pair of intrinsic muscles.

The skull has well-formed basipterygoid processes, but no occipital foramina or supra-orbital impressions. In Metopidius the radius is extraordinarily enlarged (see fig. 70, p. 125). In the remaining genera there is no such modification of the bone, but there is a metacarpal spur, which may be of the same use, i.e. for fighting. In Parra the clavicle is at its articulation further from the procoracoid than in the Charadriidæ, and the sternum has only one pair of notches. Five ribs reach it.'

The single genus Chionis,2 of antarctic range and somewhat gull-like form, makes up the family Chionididæ.

There are twelve rectrices.

The skull is peculiar in that the grooves for the supraorbital glands end in a large foramen on each side, which is

The bones of Parra albinucha are described and figured by MILNE-EDWARDS, Hist. Madagascar.

The peculiar sheath which covers the base of the bill and the nostrils (whence Sheathbill') is declared by STUDER to be developmentally different from the tube of the Tubinares.

formed by the union of the lacrymal with a process of the frontal, forming a continuous bony bar. As has been already mentioned, Edicnemus shows a very considerable approach to this state of affairs. So too, as I interpret it, do the quite typical charadriid Vanellus and Eudromias. In these birds the grooves for the supra-orbital glands do not, as they do in Limosa and Recurvirostra, border the margin of the orbit. They are situated at some distance from it, and each ends in a very small foramen, bordered in front by the ankylosed lacrymal, which I take to correspond to the large foramen of Chionis.

There are no occipital foramina or basipterygoid pro

cesses.

The cervical vertebræ are fifteen, of which the last three bear discrete ribs; six ribs reach the two-notched sternum, and there is one behind. The clavicles have no hypocleidium, and end a long way in front of carina. The coracoids are not in contact at sternal articulation.

The muscle formula is ABXY+.

The syrinx of Chionis is not widely different from that of other Limicolæ, and exhibits, as will be seen from the following description, no particular resemblance to the Galli. As is the case in so many Limicolæ, the intrinsic muscles end as such some way in front of the bifurcation of the windpipe, though they are continued on to the bronchi by fibrous tissue. They end in Chionis upon the fifth tracheal ring counting from the last.

The last four tracheal rings are more or less closely united to form an ossified box. The first bronchial semi-ring to which the fibrous continuation of the intrinsic muscles is attached is the widest (from before backwards) of the rings of the windpipe, and is deeper than the bronchial semi-rings which follow.'

The following are the principal memoirs dealing with the anatomy of this bird: EYTON,Note on the Skeleton of the Sheathbill,' P. Z. S. 1858, p. 99; A. REICHENOW, 'Osteologie von Chionis minor,' &c., J. f. O. xxiv. 1876, p. 84; SHUFELDT, The Chionidæ : a Review of the Opinions on the Systematic Position of the Family,' Auk, 1893, p. 158, and in Contributions to Comparative Osteology,' &c., J. Anat. Phys. 1891, p. 509; KIDDER and COUES, 'A Study of

It is usual to separate the two genera Thinocorus and Attagis, both South American birds, into a family, Thinocorida. In contradistinction to their allies they are graineating birds, connected with which habit is the presence of a crop, an absolutely distinctive character so far as the present group is concerned. Their anatomy has been chiefly studied by GARROD. The differences which distinguish them from

FIG. 170.-SKULL OF Attagis Gayi (AFTER GARROD).

other Limicolæ are neither great nor numerous. In the skull the basipterygoid processes are absent, and the vomer is broad and rounded in front as figured by PARKER; 2 the skull, in fact, as has been mentioned on a previous page, is ægithognathous rather than schizognathous. There are no occipital foramina, Chionis minor,' Bull. U.S. Nat. Mus. iii. 1876, p. 85; R. O. CUNNINGHAM, On Chionis alba,' J. Anat. Phys. 1870, p. 87; BLAINVILLE, Mémoire sur la Place que doit occuper le Genre Chionis,' Ann. Sci. Nat. 1836, p. 97; STUDER, Forschungsreise S. M. S. Gazelle,' Bd. iii. Zoologie u. Geologie,' p. 107.

'Notes on the Anatomy and Systematic Position of the Genera Thinocor us and Attagis,' P. Z. S. 1877, p. 413.

2 On Egithognathous Birds,' Zool. Trans. vol. x.

but the supra-orbital impressions are present. The maxillopalatines are very far apart, and besides being short are swollen instead of being leaflike plates. The same pseudoholorhiny that characterises the Glareolidæ is also found in the present family. Five ribs reach the sternum. The coracoids are quite separate at their insertion on to sternum. The muscular formula of the two genera is the complete one ABXY+.

In Thinocorus rumicivorus the syrinx has a pair of lateral muscles, which are attached to the fourth incomplete ring when seen from in front. This is probably the first bronchial, the last three tracheal rings being thus incomplete.

Glareola, Cursorius, Pluvianus, and Dromas, all Old-World genera, are included in a separate family, Glareolidæ, which GARROD regarded as very near akin to the Thinocorida.1 As in them, basipterygoid processes and occipital fontanelles are absent, and impressions of supra-orbital glands present. The muscle formula too is complete, and the syrinx has intrinsic muscles.

Except in Cursorius there is a hallux. FORBES, with some reason, has united into a group Pluviales, equivalent to the rest of the Limicolæ, this family, together with the Thinocorida and Chionididæ, mainly on account of the above combination of skull characters found in no other Limicolæ.

As in them also there is pseudo-holorhiny, the bony nostrils, though extending back beyond the nasal process of the premaxilla, being distinctly rounded off.

Pluvianus, however, has typically holorhinal nostrils.

In Cursorius the grooves for nasal glands are converted into elongated foramina by a fusion between adjacent processes of the skull.

The gulls form another distinct family, Laridæ, containing the genera Larus, Lestris, Sterna, Rhynchops, Anous, and Gygis.

The skull is schizorhinal and schizognathous, without 1 LINN.EUS placed Glareola in genus Hirundo, SUNDEVALL in Caprimulgidæ.