210 MR. W. A. FORBES ON THE [Feb. 7, 
It is not unusual in birds to find a small irregular vipple-like 
projection guarding the entrance to the pylorus ; and it is, I am in- 
clined 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. As in the latter, there 
are two ceca, *2 inch long, whilst in most specimens of P. anhinga 
one only has been observed’. As in P. anhinga, the large intestine 
is peculiarly long, measuring 55 inches; the small intestine has a 
length of 30 inches. The bursa fabricii, I may add, in the present 
specimen (a ¢) 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 ambzens 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. nove-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* in P. anhinga, are also ossi- 
fied, 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 persis- 
tent ‘‘ 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 loco- 
motion is effected entirely by the feet, the bird pursues his prey 
(small fishes) with a peculiar “ darting ” or jerky action of the head 
' Ina specimen of Plotus anhinga that has passed through my hands since 
this paper was read there was, in addition to a single cecum of the ordinary 
size, a much more rudimentary one developed on the other side of the intestine. 
2 L.c. pl. xviii. fig. 2a. 
