208 PROCEEDINGS OF THE ACADEMY OF 



Laridie. la the other sub-families of Procellariidx it is scarcely more than an 

 immovable sessile claw. When present, its condition varies. Withoutexception, 

 it is raised above the level of the anterior digits ; but the elevation is slight in all 

 Totipalmi, among which are found the most arboricole swimmers, just as in 

 Ardcidce, of Cursores, which are pretty good perchers. Its direction is ordi- 

 narily straight backward ; to which the best exception is seen in its oblique 

 inward position in all Stegnnopodcs, where, likewise, this toe is much longer 

 than elsewhere. In Spheniscidsc the hallux is very small, lateral and elevated. 

 As to its connection with the other toes or the tarsus, we find several modi- 

 fications. In the first place, we have the condition in J'rocellariinee. of sessile 

 inmobility. Next a lengthening and freeing, as in Ltiridce and Atiatinx, 

 Then with slight increase, or none, in length, there may be a broad membra- 

 nous lobe depending from it, e. ff.. FuligulitKP, I'odicipidce. This lobe, again, 

 may unite it at base with the tarsus or inner toe, as in Coli/mbidx ; a condition 

 intermediate between the foregoing modification and the only other one to 

 be noticed, viz., that characterizing the Stega/wpodes, when the very long hind 

 toe completes, by webbing to the claws with the inner one, the totipalmate 

 foot. In most or all those cases where the hallux aborts, I think its acces- 

 sory metatarsnl is still to be found beneath the skin of the tarso-metatarse. 

 I have never sought for it in vain.* 



Palmation is undoubtedly the prime characteristic of the swimming foot; 

 yet it does not always obtain. Lobation marks one whole family (the Grebes.) 

 But in Podilymhus, at least, there is a sort of compromise between the two 

 styles ; the toes being perfectly lobed, yet webbed at base. More or less im- 

 perfection of the webs in truly palmate forms exceptionally occurs. Ilydro- 

 chelidon fissipes, e. g., has the webs so deeply incised that it is scarcely more 

 palmate than sucli grallatorial genera as Symphemia, Ereimetes, &c. Some 

 Anserine genera are defective in this respect. But ordinarily the free margin 

 of the two or three webs departs but little (and that in concavity) from a 

 straight line between the ends of the toes; it is sometimes a little convex. 



The claws as a rule offer nothing of importance. They are small, short, 

 stout, little curved, not very acute. One or two genera of Alcidoi have a claw on 

 the second toe differing in all these respects from the others ; it is ordinarily, 

 also, laid fiat, not upright. Rarely the middle claw is dilated and pectinated 

 (Tachype/es) us in tferons. Goat-suckers, &c. The Grebes offer exceptional 

 claws ; these are broad, flat, and squarish in shape, much like human nails. 

 Rissa tridaciyla offers perhaps the only instance of a toe without a well formed 

 claw. 



The bill of Natatores is so variable in all its features that it is best consid- 

 ered under heads of the several orders and families. I may remark here that 

 it appears under two principal forms: lamellate in all Anatiformes and one or 

 two genera of Petrels; simple in all other swimmers ; but in these its tomia 

 may be serrate. In a great number of cases, it bears a nail at the end, of 

 varying size, large or small, and in either case liable to be either very distinct 

 or lost by fusion. This nail, it should be observed, is an affair of the horny 

 covering altogether ; not dependent upon the condition of the premaxillaries. 

 The horny case is ordinarily continuous ; but sometimes, as in Jaegers and 

 Petrels, it consists of many pieces. f In Anatiformes it is softer, more like 

 ordinary skin than elsewhere, whence ^^ Dermorhynchi " as a name of the 

 family. 



Anaiidiv, Laridic, ProceUaritdx and Podkipidir are cosmopolitan ; but Petrels 

 abound most and in greatest variety in Southern seas. Most Steganopodes are 

 wide-spread, but Tachypttidte. Phneihontidae and Plotidic are chiefly tropical. 

 C'oli/mbidce belong to the Northern Hemisphere. Alcidx are Palte-Ne-arctic, 

 'focussing in the North Pacific, replacing Spheniscida;, which are exclusively 



* So, also, I find it in Calidris arenaria, a. 3-toed .sandpiper, in tlie jJCgialites, Ac. 



tCf. the writer's "Review of Procellariidie,''^ part v, Pr. A. N. S., Pliila., May, 1865, p. 175. 



[Dec. 



