NATURAL SCIENCES OP PHILADELPHIA. 155 



HlPPOLYTE GRACILIS. 



This is the most slender species which has come under our notice. The cara- 

 pax is crested at the anterior third ; there are no supra-orbital spines, but the 

 antennal and pterygostomian spines are present, the latter spine being high 

 in position from the narrowness or little height of the carapax. Rostrum 

 exceedingly slender, scarce higher than wide, curved, a little longer than the 

 carapax, and armed with four teeth over the eye ; elsewhere smooth to the 

 tip ; below there are four minute distant teeth. The antennula; are rather 

 long, the thick flagellum reaching to the extremity of the rostrum. Anten- 

 nary appendage a little longer than the rostrum. The external maxillipeds 

 reach to the middle of the rostrum and have no exognath ; the epignath per- 

 haps exists, but we have been unable to discover it in our specimens. The 

 feet are very slender, and none of them have an epipod. The abdomen is 

 very long and strongly geniculated. Third segment compressed aod promi- 

 nent, as in Pandalus ; penult joint much elongated. Length lj inches. 



Fbund in deep water. 



Idothea Whitei. 



Body slender ; sides slightly convex; head large. Outer antenna? nearly 

 two-thirds as long as the body ; the flagellum equalling the peduncle in 

 length and composed of from sixteen to eighteen joints. First thoracic seg- 

 ment short, less than two-thirds as long as the second. Abdomen segmented 

 as in /. Wosnessenskii and the others of this group ; it is one-half longer than 

 broad, slightly narrowitfg posteriorly, with the extremity rounded, truncate, 

 and bluntly acuminated at the middle. Feet moderately stout. Color yel- 

 lowish, minutely punctate with dark gray. Length of body 0-81 ; length of 

 abdomen 0-27 inches. 



It is allied to /. Wosnessenskii, but is very much more elongated. It differs 

 from I. media, following Dana's description, in its much longer antennae. 



We have dedicated this species to Lieut. J. W. White, who commanded the 

 Revenue Cutter in the Sound while the Boundary Survey was in progress, 

 and who rendered essential aid to the Naturalists of the Survey, by dredging 

 many of the most interesting novelties which were obtained. 



Idothea urotoma. 



Body nearly linear, nearly five times as long as broad, broadest at the sixth 

 thoracic segment. External antennas a little more than one-half as long as 

 the body ; last two joints of the peduncle subequal ; flagellum a little shorter 

 than the peduncle and ten-jointed. Abdomen consisting, as in the others of 

 the group, of three joints, with the partial separation of a fourth ; subrectan- 

 gular with convex extremities, and scarcely less broad at its truncate poste- 

 rior extremity than at the anterior. The posterior extremity is peculiar in 

 shape, the angle on either side projecting strongly, and separated by a notch 

 from the convex or subtriangular middle portion, which bears a small tooth 

 at the middle. The opercular abdominal feet which cover the branchial or 

 swimming feet are large, nearly covering the entire under side of the abdo- 

 men. Thoracic feet slender. Length of the body 0*75 ; greatest breadth - l7 ; 

 length of the abdomen 0-20 inch. 



We find no note of the depth of water in which this species was dredged. 



AEGA BELLICEP3. 



Smooth, subelliptical, and pointed anteriorly. Head with a small, short, 

 blunt, rostriform process over the base of the superior antenna?. Eyes ovate, 

 very large, but distant, and beautifully granulated (facetted). Thorax rather 

 broad ; segments each marked with scattered impressed punctae, mostly in a 

 transverse row. Abdominal segments five in number, the terminal one scuti- 



1864.] 



