3i8 STALK-EYED CRUSTACEA 



being more elevated, and situated on the posterior margin), 

 and there is usually a more or less distinct protuberance 

 on the pterygostomian region. The front is concave, and 

 does not project beyond the anterior margin of the buccal 

 cavity. The orbits are very small and circular, with 

 usually three deep marginal fissures, and with a rather 

 large inferior hiatus. Eyes very small. Internal antennse 

 somewhat obliquely plicated. External antennae with 

 a slender basal joint, which scarcely reaches the front. 

 The external maxillipedes cover the buccal cavity, and 

 the fourth joint is triangulate and acute ; the external 

 appendage is rather broad, about as broad as the 

 endognath, and its external border is slightly arcuated. 

 The first pair of legs is subequal in the male, and some- 

 times considerably elongated ; the fourth joint sub- 

 cylindrical and sometimes exceeding the carapace in 

 length ; palm subcylindrical or compressed, not dilated ; 

 fingers rather robust, compressed, and distally acute ; 

 walking legs are relatively small, with the last joint 

 styliform. The abdomen, in the male, is usually four- 

 jointed, with all the segments except the first, second, 

 and last coalescent. 



Synopsis of the Species. 



A. Three spines on the posterior part of the cara- 

 pace. 



a. Carapace covered with granulations. 



a'^. Carapace regularly curved. — {^P. punctata}) 



b^. Carapace gradually and obtusely dilated anteriorly. 

 — (P. latreillii.) 



c^. Carapace almost angular anteriorly. — i^P. laiiiar- 

 ckii.) 



B. Three spines upon the external border of the 

 carapace. — {P. lichtenstenii.) 



