NATURAL SCIENCES OF PHILADELPHIA. 203 



would be interesting to know whetlier they are altrices or praecoces, and how 

 far the pah^te agrees with that of Geranomorphie. 



The " naturalness " of the division as a sub-class is sustained in a satis- 

 factory if not conclusive manner, by the large number of types that Na- 

 tatores include under natatorial modification ; the open passages that lead 

 from it to the other groups ; the number of points where other groups in- 

 fringe upon it ; and especially the highly instructive way in which its four 

 primary subdivisions repeat each other. I shall endeavor to point out the 

 principal of each of these. 



The passage from anserine swimmers to heron-like waders is so obviously 

 through and by Fhoenicopterus, that the poiut need not be dwelt upon. 



The passage from totipalmate swimmers to the same waders is unques- 

 tionably through the Pelecanidie and Cancromidfe. The affinities of Balieruceps 

 and Cancroma among herons, with pelicans, have long been recognized and 

 universally allowed. 



The passage from urinatorial swimmers to certain of the Grallee takes place 

 from the poiut Podicipidse, through Heliornithidie, to fulicarious or paludicole 

 waders, and from the same point through Phalaropodidfe to scolopacine or 

 limicole waders. In each of these cases we have almost the only — if there 

 be indeed any other — examples of the lobiped structure — a comparatively 

 rare modification of the swimming foot. The phalaropes, besides being ex- 

 cellent swimmers, are further exceptional in their own sub-class in the texture 

 of the plumage, which is completely duck-like. 



The passage from longipennine swimmers to Grallre, if not so evident, is 

 nevertheless clear, in the osteological and pterylographic characters that are 

 respectively more or less common to a gull, e. g., and the plover or snipe-like 

 waders, as Nitzsch and Huxley have pointed out. Certain small petrels again, 

 as Oceanifis, Fregetta and Pelayodroma, are exceptionally " grallatorial " in 

 length of leg. 



The waders coming next to swimmers, it is not to be expected that higher, i. e. 

 rasorial, Cursores, still less a further removed sub-class, Insessores, should 

 afford direct transitions ; but as I shall endeavor to show, the swimmers give 

 analogues to the main types of each of these sub-classes. Foreshadowing of 

 the mammals in birds does not occur within the range of Nnlatores, unless 

 the duck-like bill of Ornithorhynchus is a case in point. It really takes place 

 at the point Ratitx. It is among NatuloreH,&s the lowest birds, that the coun- 

 terfeit of another vertebrate type is found. The mocking analogy with fish 

 is complete in the penguins. 



The raptorial modification of Na/atores is seen in the sub-family Lestridinie 

 of Laridx. The habitus of these is that of land birds of prey — a univer- 

 sally recognized resemblance. In their food the Jaegers are vulturine. Phy- 

 siological analogy is borne out by physical characters. Jaegers are the only 

 cered swimmers, as Accipitres are the principal cered perchers. The claws 

 of Lesfndime are more " raptorial " than those of any other swimmers. A 

 singular rugosity of the tarsi is shared by the Jaegers and the most aquatic 

 genus of Accipitres — Pandion. 



The rasorial modification occurs in urinatO'rial swimmers. All these have 

 short, more or less concave, wings that are rapidly vibrated, and fly with 

 great impetus ; very gallinaceous features. Some Alcidie employ the char- 

 acteristic habit of Gailinm in constructing their nests ; rasorial has developed 

 into fossorial. Other auks, notably Phalaridines, instantly recall quails by 

 their general aspect; a species has been named from the circumstance. The 

 bill of 3Iergulus repeats a partridge's. Absence of tlie hallux that marks all 

 Alcidie, though sufficiently frequent in scolopaceous Cursores, is rare among 

 the alectoromorph Cursores; yet it characterizes a family — Turnicidie. One of 

 the rarest modifications, viz., abortion of rectrices, that marks a family of 

 Urinatores, is only again found in soiue representatives of a rasorial family — 

 Crypturidse. 



Tubular nostrils are not a very common feature. It is the prime characteris- 



1869.] 



