650 



THE VOYAGE OF H.M.S. CHALLENGER. 



Plesionika brevirostris, n. sp. (PL CXIII. fig. 5). 



Eostrum a little shorter than the dorsal length of the carapace ; free from spines on 

 lower margin and on the upper anterior to the crest, which consists of six teeth. The 

 rest of the carapace and pleon is smooth. 



First pair of antennae having the flagella as long as the animal. 



Second pair having the flagellum a little longer than those of the first ; scaphocei'ite 

 subequal with the rostrum. 



Second pair'of gnathopoda reaching a little beyond the distal extremity of the rostrum. 



Pereiopoda long and slender ; first pair a little longer than the second pair of 

 gnathopoda, but more slender. Second pair of pereiopoda a little shorter than the first 

 and more robust ; the carpos long and multiarticulate. Third, fourth, and fifth pairs 

 increasing in length posteriorly, the last reaching beyond the extremity of the rostrum 

 to a distance equal to the length of the carapace. 



Telson dorsally depressed in the median line, shorter than the lateral plates of the 

 rhipidura. 



Habitat— Station 200, October 23, 1874 ; lat. 6° 47' N., long. 122° 28' E. ; between 

 the Philippine Islands and Borneo; depth, 250 fathoms; bottom, green mud. One 

 specimen, female. Trawled. 



Observations. — The specimen was laden with numerous ova, of which I approximately 

 counted 6000 ; it was trawled with considerable numbers of Plesionika semiLvvis, with 

 which it appears to closely correspond in general aspect and in all parts, excepting in the 

 shortness of the rostrum and the absence of teeth from the lower margin. It is not 

 improbable that it is only an extreme variation in form of the latter species due to some 

 accidental cause, and illustrating the early stage of a specific variation. 



Nothocaris, 1 n. gen. 



Carapace smooth ; dorsally crested over the gastric region and produced to a long 

 rostrum ; armed on the crest with rigid teeth and movable spines ; frontal margin 

 having an antennal and fronto-lateral tooth. 



1 voSo;, illegitimate ; r.xptz, shrimp. 



