ISISTIUS BRASILIENSIS. 37 



In the bulbils of the heart there are tiiree rows of valves, Plate III., 

 figs. 4, 5. 



Together the stomach and the intestine form a straight tube hardly 

 longer than the distance from the gullet to the vent; they overlap at 

 tlie pylorus only about one ocular diameter. The stomach is a long 

 straight sac occupying five eighths of the length of the abdominal cham- 

 ber; the intestine contains a spiral valve of about nine circuits, and has 

 an elongate subcylindrical cajcal appendage, Plate III., fig. 3. The pancreas 

 is two-lobed and lies against the stomach on the forward extremity of the 

 intestine. 



The shoulder girdle is very slender and flexible. Pro-, meso-, and meta- 

 pterygia in the pectorals have coalesced so as to form a subquadrate plate 

 articulated with the girdle. The small distal extremity of the proptcrygium 

 and that of the metapterygium have the appearance of radials; the latter 

 bears six radials, several of which are segmented into two series. On the 

 mesopterygium there are five radials, each divided near the middle of its 

 length, Plate III., fig. 6. In the skeleton of a ventral fin, Plate III., fig. 1, 

 thei'e is a strong basal cartilage, in three segments, bearing about a dozen 

 radials, each also in three segments. The anterior radial, against the pelvic 

 cartilage, was probably formed by coalescence of several radials. 



The dorsal fins are small and similar in size and shape ; their distance 

 apart is equal to the distance of the posterior from the caudal fin or to the 

 width of the head ; the origin of the anterior dorsal is three fifths of the dis- 

 tance from the snout to the end of the caudal, its posterior angle is acute 

 (mutilated in the specimen drawn), and the hinder part of the base is above 

 the bases of the ventrals. The pectorals are small, nearly as wide as long, 

 their angles are rounded off, and their bases are low on the side of the body. 

 The ventrals are smaller than the pectorals, they are about twice the size of 

 the dorsals, and they are shorter than the space between these fins and 

 almost entirely below it. The caudal fin is short and deep, its lower lobe is 

 two thirds as deep as long ; the upper lobe is longer, subtruncate or convex 

 on the hinder margin, and separated from the lower by a notch at the end 

 of the vertebral column ; the caudal pedicel is wider than deep, its depth is 

 less than one fourth of that of the body, and it has a short low dermal 

 keel on each side below the lateral line. 



There is probably no shagreen better adapted for scouring purposes than 

 that of the shark here described ; its fineness makes it less desirable for 



