684 THE VOYAGE OF H.M.S. CHALLENGER. 



is smooth and free from teeth, excepting two or three small points near the apex. The 

 frontal margin is furnished with a tooth at the outer angle of the orbit corresponding 

 with the position of the first antennal tooth, beyond which there appears to be no 

 other tooth. 



The pleon has the somites subequal, the sixth being cylindrical, a little longer and 

 narrower than, but not so deep as, the fifth and preceding somites. The third somite 

 carries a tooth at the posterior extremity of the dorsal surface that is as long as the sixth 

 somite or as the telson, which tapers to a sharp point. 



The ophthalmopoda are about one-fourth the length of the rostrum, slightly pear- 

 shaped and about half as thick as long. 



The first pair of antennae (fig. lb) has the first joint a little longer than the 

 ophthalmopoda, the second and third very short, cylindrical, and supporting two slender 

 flagella that reach nearly to the extremity of the rostrum. 



The second pair of antennae (fig. lc) has the second joint of the peduncle produced to 

 a sharp tooth at the inner distal extremity, and carries a long and trigonal scaphocerite, 

 the distal extremity of which runs to a sharp point, the outer margin being armed near 

 the middle with three strong sharp teeth, and the inner fringed with recurved teeth and 

 fine ciliated hairs. The third joint is obliquely articulated on the inner side of the 

 second ; it is cylindrical, and articulates at its extremity with the fourth joint, which 

 carries at its extremity a long and slender flagellum, the basal articuli of which are 

 fused together for a distance equal to about half the length of the scaphocerite. 



The oral appendages have not been examined, as the specimen is a solitary one and 

 the species of the genus that are known are not numerous. 



The first pair of pereiopoda is slender and styliform, and carries a basecphysis. The 

 second pair is scarcely as long as the first, more robust, and terminates in a well- 

 developed chela of which the propodos is thick and the fingers shorter than the palm ; 

 this pair also appears to be furnished with a basecphysis. The third and fourth pairs are 

 slender, longer than the preceding, terminate in a rather long and slender dactylos, and 

 carry a rudimentary basecphysis. The fifth pair shows no evidence of a basecphysis and 

 terminates in a dactylos that is shorter than those of the preceding pairs. 



The pleopoda are biramose ; those of the sixth pair are subequal in length and do not 

 reach beyond the distal extremity of the telson. 



Thalassocaris stimpsoni, n. sp. (PI. CXVII. fig. 2). 



Carapace dorsally smooth, anteriorly produced to a rostrum that is straight, laterally 

 compressed, and about half the length of the carapace. 



Pleon smooth except for a tooth on the posterior margin of the third somite. The 

 sixth somite is a little longer and narrower than the fifth. 



