MUSEUM OF COMPARATIVE ZOOLOGY. 95 



The inner lamella of the iiropod is slightly longer than the sixth somite, 

 lanceolate, and about four times as long as broad. The outer lamella is just 

 about as long and wide as the antennal scale, but is broader at the tip. 



There are only three specimens in the collection, all apparently females, and 

 all more or less imperfect. The largest specimen, from Station 323, gives the 

 following measurements, which, on account of the soft condition of the speci- 

 men, are more or less approximate. 



Length from tip of rostrum to tip of telson 42.0mm. 



Length of carapax including rostrum 16.3 



" rostrum .......... 5.5 



" antennal scale . 8.0 



" external maxilliped ........ 19.0 



" first pair of legs ........ 12.0 



" second pair of legs 18.0 



« third pair of legs 22.0 



" sixth somite of abdomen 6.2 



Height of " " " 3.3 



Length of inner lamella of uropod 6.5 



Breadth " " " 1.6 



Length of outer lamella of uropod ....... 8.2 



Breadth " " " 2.0 



Possibly none of the specimens are fully grown, but all have apparently 

 attained the characters of the adult. The smallest specimen, less than 30 mm. 

 in length, does not differ, except in size, from the largest. 



The genus Pencrus, even after the subdivisions recently made by Bate, in- 

 cludes species differing widely in the structure of the articular appendages and 

 in the arrangement of the Ijranciiioe, but the genus here proposed appears to 

 differ from all these species in the small and narrow terminal segment of the 

 mandibular palpus, the rudimentary character of the exopods of the external 

 maxillipeds and legs, the number and arrangement of the branchiae, and the 

 membranaceous character of the integument. From the typical species of 

 Penceus it differs moreover in the short and unsegmented endognath of the 

 first maxilla and in the sulcation and armament of the carapax. The species 

 here described is possibly closely allied to, or even congeneric with, Haliporus 

 Bate, which, however, is so imperfectly characterized, and the four species 

 referred to it so briefly described, that it is impossible to determine its affinities 

 with any certainty. 



