1886.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 313 



iimer joint of the anterior auteniite is nearly three times as long as broad, 

 broadest near the onter end, and strongly and regularly curved from 

 the outer edge of the anterior emargination to the postero-lateral an- 

 gle, this entire curved margin bearing numerous long and rather stout 

 pai)illie. The outer joint is a little more than one-third the length of 

 the basal, and about twice as long as broad, its distal end with a cluster 

 of small setae; two similar setiB project from the posterior margin near 

 the outer end. The terminal joint of tke second antennre bears two 

 small, slender spines on the basal portion, the distal portion being stout 

 and slightly curved. 



The swimming feet of the first pair vary somewhat in shape in differ- 

 ent specimens, but the long flexible spines are the same in number and 

 similarly placed in all the specimens that have been examined. In the 

 specinuMi represented on plate VII, fig. 1, there is on the middle portion 

 of the <juter side of the outer ramus a prominent raised area projecting 

 laterally, and with convex surface, not existing in the other specimen fig- 

 ured (fig. 2). The same character occurs, however, on specimens from 

 all three species of sharks. The two rami of the second pair of feet are 

 of subequal length, the outer being slightly shorter than the inner. 

 The terminal joint of the outer ramus is about two- thirds as long as 

 that of the inner, quite regularly oval in outline and with nine marginal 

 spines, arranged mainly along the end and the inner margin, the four 

 outermost being much the largest. The terminal joint of the inner 

 ramus is about twice as long as broad, and broadens gradually from 

 the base to near the end; it bears five slender spines on the inner 

 margin at the tip, and immediately in advance of them, on the inner 

 margin, there is occasionally an additional minute spine. The four 

 outermost spines are subequal in size and curve outwards; the fifth is 

 smaller and curves inward. 



Of the third pair of feet, both rami are about equal in length, the 

 terminal joint of the outer ramus being but slightly shorter than that 

 of the inner. The spines of the terminal joint of the outer ramus, in 

 specimens from the sand- shark, are eight in number and vary some- 

 what in size, as shown in the drawing, and all but one curve outward; 

 on the corresponding joint of the inner ramus, the two outermost si)ines 

 only curve in the same way. In specimens from the dog-fish and At- 

 wood's shark, both rami are somewhat smaller than in those from the 

 sand-shark, and the innermost terminal spine of the inner ramus is want- 

 ing, leaving only the two curved spines; on the terminal joint of the 

 outer ramus, the innermost spine is lacking in the dog fish specimens 

 and occasionally in those from the sand-shark, and this and tiie next 

 succeeding one are not found in the specimens from Atwood's shark. 

 Inside of the rami there is a large, well-rounded, lobe-like extension of 

 the basal joint, which is often much larger than represented in the figure. 



The fourth pair of feet vary considerably in size and shape, but are 



