CARCINOLOGICAL STUDIES. 121 



with two short spines on the anterior margin of its external 

 surface. The flagella are about as long as or a little longer 

 than the body. Outer foot-jaws elongate. First pair of legs 

 short, stout and equal. Carpopodite short, conical, 

 deeply excavate at its distal extremity. Legs 

 of the second pair slender; carpopodite seven- 

 articulate, with the joints nearly equal in length. Pos- 

 terior three pairs rather short and stout. 



As Stimpson, and lately also Spence Bate, has established 

 several new genera for the species of the old genus Hippolyte, 

 I am obliged to create also a new genus for the new 

 species I have to describe. Hetairocaris is most closely 

 allied to the genus Hetairus Sp. Bate. Both genera present 

 a supraorbital and an antennal tooth on the fronto-lateral 

 surface of the cephalothorax and in both the carpus of the 

 second pair of legs is seven-articulate. In the new genus , 

 however , the carpus of the first pair of legs is short and 

 deeply excavate, quite as in Hippolyte s. s. Sp. Bate, the 

 lower margin of the rostrum is entire and the fronto-lateral 

 angle of the cephalothorax is rounded ; the outer maxilli- 

 pedes are also more elongate. The genus Hippolyte, as 

 restricted in the beautiful Report on the Challenger Ma- 

 crura , is armed , like Hetairocaris , with a supraorbital 

 tooth , and the carpus of the first pair of legs is also short 

 and deeply excavated , but the carpus of the second pair 

 is triarticulate , the external maxillipedes are shorter , and 

 two antennal teeth seem to occur in this group on the 

 fronto-lateral surface of the cephalothorax. 



The genus Hetairocaris represents the Atlantic genus 

 Hetairus in the Pacific Ocean. ') 



1) Spence Bate thought that the Japanese Hippolyte rectirostris Stimps., a species 

 which is closely allied to Hetairus Gaimardi, ought to he referred to the genus 

 Retairus, but I may observe that Stimpson makes no mention of the existence 

 of a supraorbital tooth, which, however, is characteristic of the genus ^e;ifatV?/«. 



N otes from the Leyden ÜMuseum , Vol. XII. 



