268 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
SPLANCHNOLOGY. 
The viscera are arranged in the abdominal cavity in a somewhat pe- 
culiar manner in that the black pigmented layer of the mouth and 
throat is continued back over a blind, saccular prolongation of the walls 
of the pharynx and csophagus, the latter being so greatly widened as 
to scarcely be evident, except as defined by its relative position with 
respect to the branchiz. This peculiar arrangement has given an un- 
expected significance to the generic name which we have proposed: 
While there is no very evident csophageal constriction, Loth it and 
the pharyngeal part of the alimentary tract are very short, owing to 
the great reduction of the branchial apparatus. 
The thin membranous parietes of the mouth and throat are thrown 
into numerous longitudinal, approximated, parallel folds, in harmony 
with the fact that the throat and mouth are very distensible. This 
wrinkling of the parietes of the pharyngeal region is apparent above the 
gills, which evidently open internally in the ventral part of the pharynx. 
A darkly pigmented cecal prolongation of the throat begins just 
above and behind the gills, and is lined with a thick deeply plicated 
secretory epithelium, the whole sack extending as far back as the first 
half of the body cavity; at the anterior lateral portion of this pigmented 
sack the widest, thick-walled part of the intestine arises on the right side 
and extends backward uuder the dark- walled czeal pouch along the mid. 
dle line between the thick and symmetrically disposed liver, which lies 
against either side of both the dark pouch and the first portion of the 
intestine, and extends for about half the length of the abdominal cavity. 
Behind the liver the intestine becomes suddenly narrower, and has two 
flexures, but is not very sharply bent upon itself. 
The pigmented cecal part of the alimentary tract seems to be the 
stomach, from which it is probable that the food is passed after partial 
digestion to the thick-walled anterior portion of the intestine proper, 
lying just below it and opening into it at its anterior part. 
The mode in which the food is collected is probably as suggested be- 
fore, namely, by filling the mouth with water containing small organ- 
isms which are retained and left in the pharynx above the gills as the 
water is strained through the latter. The wrinkles in the oral and 
pharyngeal integument would indicate that the latter probably contains 
scattered muscular fibers and is itself contractile. 
The abdominal cavity is separated from the cardiac by a septum, in 
front of which there is a well-developed heart of the usual type with an 
atrial sinus, ventricle, and bulbus aorte. The heart lies in a very 
thick-walled pericardial sac. 
No air-bladder or rudiment of such a structure has been discovered 
in our specimens. 
The renal organs lie in the hinder part of the abdominal cavity, ex- 
— 
