ON THE ANATOMY. OF PLOTUS ANHINGA. 341 
tunity of stating elsewhere*, that in Fregata aquila the semitendinosus 
is entirely absent, as in the Accipitres, whilst in Phaéthon it has an 
accessory head as well as a considerable bulk itself, these facts tending 
strongly to verify Brandt’s division of the Steganopodsf into three 
well-differentiated groups, of two of which the above-named genera 
are the only examples. 
The alimentary canal of the Darter presents features of especial 
interest, as in its stomach there is a modification in the structure of 
the proventriculus not referred to in zoological works generally. It 
is fully described by Mr. Macgillivray in Audubon’s “ Ornithological 
Biography,” { where an excellent figure illustrates the account. Mr. 
Macgillivray also accurately describes most of the other viscera. He, 
however, omits to refer to the hairy mat in the second stomach, 
which latter viscus, he strangely says, is soft and smooth inside. The 
observations here made, which are in accordance with those of Mr. 
Macgillivray, cannot be considered de trop, as the extremely abnormal 
conformation he describes required verification before it could be 
accepted as not being merely an individual peculiarity. 
The tongue, as an independent organ, does not exist. It is very 
small in all Steganopods, but free at its anterior extremity; smallest 
proportionally in Pelecanus. In Plotus, however, it is not free at its 
apex, it forming merely a longitudinal groove along the middle of the 
fioor of the mouth, and ending abruptly behind by a small transverse 
slightly projecting ridge, 2} inches in front of the rima glottidis, which 
is evidently the rudiment of the base of the organ. The hyoid cornua, 
1} inch long, running in the faucial membrane, here meet and blend. 
There is no crop; the cesophagus, however, is very dilatable. The 
proventriculus does not form a zone, as is the rule; nor does it form a 
patch, as in Struthio, Rhea, Chauna, and a few other birds; but it 
forms a special gland-cavity into which the individual constituents of 
the organ open, This cavity communicates with the digestive tuhe by 
a small orifice which is situated on the right side of the stomach, just 
below the commencement of the yellow dense characteristic epithelium 
of the stomach in birds. Plate [20] XXVIII. fig. 2, will assist in 
rendering this explanation more distinct, 
The proventricular compartment is covered by peritoneum, is 
nearly globose, about the size of a chestnut, and fixed to the right side 
of the lower end of the cesophagus. On superficial inspection it looks 
very like an enlarged spleen (that organ being subglobose in birds). 
Its cavity is very small, being much encroached upon by the great 
* “Proceedings of the Zoological Society,” 1873, p. 636, and 1874, p. 122 
(Supra, pp. 198 and 221.) 
+ “Proceedings of the Zoological Society,” 1874, p. 122. (Supra, p. 221.) 
t Vol. iv. p. 158. 
