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Show 210 MR. W. A. FORBES ON THE [Feb. 7, It is not unusual in birds to find a small irregular nipple-like projection guarding the entrance to the pylorus; and it is, I a m inclined to believe, a greatly developed condition of this structure that forms the hairy " plug " of the Old-World Darters. In the rest of its anatomy Plotus melanogaster resembles in nearly every respect P. anhinga and P. levaillanti. A s in the latter, there are two caeca, *2 inch long, whilst in most specimens of P. anhinga one only has been observed1. 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 d 1 ) 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. nova-hollandia, 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 11th cervical vertebra, which are correctly figured and described (in the explanation to the plate) by Garrod 2 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 myolo-gical characters of the neck of the Darter. But, probably from never having observed 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 a peculiar « darting " or jerky action of the head 1 In a specimen of Plotus anhinga that has passed through my hands since this paper was read there was, in addition to a single caicuin of the ordinary size, a much more rudimentary one developed on the other side of the intestine 2 L. c. pl. xviii. fig. 2 a. |