328 ON THE ANATOMY OF 



has been observed *. As in P. anhinga, the large intestine is peculiarly 

 long, measuring 5'5 inches ; the small intestine has a length of 

 30 inches. The bursa fabricii, I may add, in the present specimen 

 (a c? ) had the ordinary relations of that organ to the cloaca, opening 

 into that chamber by a small pore. There is only one carotid artery, 

 the left, as in the two other species of Plotus, the genus Pelecanus, and 

 Sula leucogastra and S. piscator, though not in S. bassana, or the other 

 Steganopodes. The patella is only grooved, and not perforated, by the 

 ambiens muscle. 



The structure of the neck in P. melanogaster is almost identical with 

 that of P. anhinga, as described and figured by Garrod. "Donitz's 

 bridge," situated, as in the other species, on the 9th cervical vertebra, is 

 well-ossified in the present specimen, as it is also in P. levaillanti and 

 P. novce-hollandice, though not in P. anhinga. 



In addition to this, the similarly-situated fibrous bands formed by a 

 specialized part of the general cervical aponeurosis on the llth cervical 

 vertebra, which are correctly figured and described (in the explanation 

 to the plate) by Garrod t in P. anhinga, are also ossified, each in its 

 median portion being converted, over a small area about the size of a 

 hemp-seed, into bone. Through the canal thus formed on each side, the 

 longus colli posterior, as well as the general mass of posterior neck- 

 muscles, passes. On examination of P. levaillanti, I find these bands 

 also ossified in that species ; in P. anhinga, as already correctly stated 

 by Garrod, they remain fibrous. There is no such ossification of the 

 cervical portion of the longus colli posterior tendon in this species, as was 

 observed by Garrod in P. anhinga; and in this respect again the 

 African and Indian species agree, and differ from their American 

 relative. 



Prof. Garrod, in the first of his papers already referred to, has fully 

 and accurately described the peculiar osteological and myological charac- 

 ters of the neck of the Darter. But, probably from never having ob- 

 served these birds when feeding, he has not pointed out the connexion 

 between this peculiar neck, with its naturally persistent " kink," of the 

 Darters and their mode of life. 



The Darters feed entirely, so far as I have been able to observe, under 



water. Swimming with its wings half expanded, though locomotion is 



effected entirely by the feet, the bird pursues his prey (small fishes) with 



P Z S 1882, a peculiar " darting" or jerky action of the head and neck, which may 



p. 211. be compared to that of a man poising a spear or harpoon before throwing 



* In a specimen of Plotus anhinga that has passed through my hands since this 

 paper was read there was, in addition to a single caecum of the ordinary size, a much 

 more rudimentary one developed on the other side of the intestine. 



t L. c. pi. xviii. fig. 2 a. 



