190 NATURAL HISTORY OF BIRDS. 



portion of the rock, and on the Little Bird." The nest is usually built of grass or 

 sea-weeds, which the birds tear off with their sharp beaks, and a single egg of a chalky 

 whiteness, but usually stained and soiled, is deposited, from which is hatched a naked 

 slaty-blue chick, soon to be covered with snow-white down. The adults are white, 

 head and neck above washed with buff, bill bluish-gray, feet slate-color with light 

 green stripes, indicating the course of the tendons ; eye yellow. The immature birds 

 are dusky, speckled all over with white spots. 



A few allied species inhabit the tropical seas of the eastern hemisphere, and a 

 group of smaller, more or less dusky-colored gannets are entirely inter-tropical. In 

 general habits they differ but little from the typical species, and altogether there are 

 at present hardly ten different forms. The fact that fossil Sulidae have been found in 

 France in miocene fresh-water deposits indicates, however, that this family formerly 

 was wider distributed and richer in forms. A miocene Sula is also known from North 

 Carolina. 



The two following families are probably more closely related inter se than they are 

 to any of the foregoing. The following are a few characters which the cormorants 

 and the darters have in common, and in which they differ from pelicans and gannets: 

 They have^ twenty vertebrae in the neck, against seventeen to eighteen; the ninth 

 vertebra is the first one pressed back preaxially, and not the eighth ; the twentieth to 

 twenty-fourth vertebra? in the cormorants, and the twenty-second to twenty-fifth 

 vertebra? in the darters, are opisthocoelous, while none have^ that character in the 

 pelicans and gannets ; the latter possess a spinal feather-space, which the former have 

 not, but these have an occipital style unknown in the others. This occipital style is a 

 triangular, elongated bone, articulating with the tubercle on the middle of the upper 

 edge of the occipital bone. The object of this process is to afford surface for the 

 insertion of " the superficial temporal muscles meeting behind the skull along the 

 median raphe, which becomes ossified to form the above-mentioned style in the adult 

 bird." A myological feature, which is not shared by the two foregoing families, is 

 that the biceps muscle of the arm sends a fleshy slip to the middle of the patagial 

 tendon of the tensor patagii longus. Finally may be mentioned the very backward 

 position of the hind limbs, which force the cormorants and darters to carry their body 

 more erect than the other members of the order. 



The cormorants, PHALACROCORACID^E, are readily distinguished from other Stegan- 

 opods by the combination of a strongly hooked bill, in shape and structure like that 

 of the frigate-bird, long neck, short wings, and rather long, rounded tail. The 

 head is often crested, and head and neck frequently adorned with thin filamentous 

 plumes, which are assumed towards the pairing season, and disappear after the 

 breeding. 



We regard this family as the central one of the order, hence the negative nature 

 of the characters including the anatomical features, the status of which is best found 

 by consulting the diagnoses of the other families. Here shall only be mentioned the 

 peculiarity of the ambiens muscle in passing through the substance of the large tri- 

 angular patella in a bony canal. 



The cormorants form a very homogeneous group of nearly forty existing forms, 

 and even the tertiary cormorants seem to be very closely allied to the typical species 

 of the present day, indicating that the group has assumed its peculiarities at quite a 

 distant period. 



On account of this uniformity, nobody who ever saw a cormorant will be in 



