Pacific Coast of North America. 327 



Head large; front produced into a prominent triangular 

 process, with rounded apex, very broad at the base, occupying 

 half the anterior margin of the head. The antero-lateral 

 angles of the head are produced in acute angles on either side 

 to a distance equal to half the length of the frontal process. 

 The eyes, which are small, are situated on the extreme lateral 

 margins of the head. The first pair of antennae are extremely 

 small, equal in length to less than half the width of the 

 head ; flagellum obsolete. The second pair of antenna are 

 also extremely short, equal in length to the width of the head, 

 with rudimentary flagellum, composed of about five joints, and 

 with peduncular joints dilated. Mandibles have the cutting- 

 part composed of five teeth; palp three-jointed. 



The thoracic segments are subequal in length, with lateral 

 edges produced, but not laciniate, and separated from each 

 other by lateral incisions. 



Caudal segment regularly rounded, with two small in- 

 cisions at the place where the uropoda are attaclied, between 

 which is a rounded lobe. Uropoda are extremely small, 

 short, nodiform. 



Legs simple, similar in structure, with biunguiculate 

 dactyli. 



Two specimens from Monterey Bay, California, were sent 

 by Mr. Heath. 



Type. No. 22583, U.S. N. M. 



This species is very close to Jceropsis brevicoriiis, but differs 

 in the following points : — the colouring of the body, which in 

 J. hrevicornis is perfectly transparent and colourless, with 

 the exception of the head, which is marked with a large 

 brown spot, while in our species the head is dark, as are also 

 the entire second, third, fourth, and seventh thoracic segments 

 and the terminal abdominal segment, the other segments 

 being colourless ; in the shape of the terminal segment, which 

 is perfectly rounded in J. hrevicornis and fringed with hairs, 

 while in our species there are two posterior incisions for the 

 reception of the uropoda, and an absence of hairs ; in the 

 larger median lobe on the anterior margin of the head ; in the 

 acuteness of the antero-lateral angles of the head, which are 

 rounded in J. hrevicornis ; in the more angular post-lateral 

 angles of the head ; and in the more angular antero- and post- 

 lateral angles of the thoracic segments. Other differences are 

 noticed from a comparison of both pairs of antennte. 



