M2 CRUSTACEA OF THE UNITED STATES. [May, 



largest acute one at the inferior inner tip, an impressed 

 longitudinal line on the outer side; hatid not broader than 

 the carpus, linear, nearly equal to the third joint, with 

 three elevated ciliated lines above, two impressed ciliated 

 ones on the outer side, beneath with long hair, and a 

 groove, which is a little c/blique, and marks the origin of 

 the short angle or fi.ger at tip, a short spine above at 

 base, finger as long as the carpus, with three or four lines 

 of rigid hairs, grooved on the outer side and glabrous 

 within; second pair of feet ciliated with long hair be- 

 neath, third joint with a prominent acute spine at base 

 beneath, and another somewhat dilated and compressed 

 at tip above, nail deeply ciliated above; third pair hairy 

 on the terminal joints, tliird joint about three-spined be- 

 neath and a little hairy; fourth 2Ci\^ fifth pairs hairy on the 

 terminal joints, nails very small and concealed by the co- 

 mose termination of the feet, those of the former closing on 

 the tip of the preceding joint, those of the latter upon a pro- 

 jecting angle of the preceding joint; abdometi glabrous, 

 segments each with a lateral, longitudinal, impressed, sub- 

 marginal line, the first, second, sixth and fifth subequal, 

 the latter shorter, third and fourth equal shortest; natatory 

 feet composed of a suborbicular peduncle, supporting 

 two deeply ciliated lamellae, of which the outer one is 

 more than as long again as the inner one, suboval, at- 

 tenuated at base and acute at tip, inner one oval, nar- 

 rowed at base; caudal lamellcs short, ciliated at tip, del- 

 toid, subequal, the inner one smaller, truncate at tip, a 

 longitudinal elevated line in the middle, and a costal outer 

 margin w^hich is slightly angulated near tne base, outer 

 ' .le somewhat rounded at tip and at the inner angle, two 



