330 PR0CEEDINC4S OF THE ACADEMY OF [^1^7, 



by the spiral valve. The diameter of the colon is much greater 

 than auy other division of the intestine, and posteriorly its boun- 

 daries are fixed by the terminus of the spiral valve, and the last 

 division of the intestine is formed. This is the rectum. It is of 

 more constricted dimensions than the colon, persisting as a short 

 simple tube to the cloaca, into which its contents are conveyed by 

 means of the rectal aperture. There is a rectal gland which is 

 confluent with the rectum. 



Liver. — Large and bulky, the left lobe greatly exceeding the 

 right in dimensions. 



Spleen. — Present in the usual position. 



Pancreas. — Developed. 



GALEID^. 



3. Galeus mustelus (Linnaeus). 



Squalus Mustelus Linnfeus, Syst. Nat., Ed. X, 1758, p. 235. 



Nos. 605 to 608. Types of Madelus equestris Bonaparte, 

 Fauna Italica, Pesci, Tomo HI, vii, 1834, 43, PI. 132, fig. 2. 

 Italy. Bonaparte Coll. (^o. 254). Dr. T. B. Wilson. 



Moidh. — Moderately large, somewhat spacious and compressed. 



Sharp teeth upon the jaws. Tongue broad, flat and free in 

 front. Inside of the mouth roughened more or less with fine 

 shagreen. 



Pharyn-v. — Spacious, elongate and compressed. The walls of 

 the branchial arches are roughened and also the floor of the 

 pharynx. Gill-openings 5 within the pharynx, which lead into as 

 many gill-pouches, and finally communicate externally by as many 

 gill-slits. The internal gill-openings, in fact the entire branchial 

 system, resembles that of Pristiurus melastomus so far as ob- 

 served. The spiracle aperture within the pharynx, anterior and 

 superior to the first gill-opening. 



CEsophagus. — Short and constricted, with the walls plicate. 



Stomach. — Rather long, spacious and bulky. There are few 

 plications upon the walls of the cardiac region. Pyloric region 

 short. 



Intestijie. — Duodenum short. Colon large and very bulky, 

 especially its median portion, and furnished with a spiral valve. 

 The rectum short and simple, terminating in the cloaca. A rectal 

 gland is developed which is confluent with the rectum. 



