REPORT ON THE CRUSTACEA MA CRURA. 477 



Observations. — Whatever form the ultimate development of this species may assume, 

 1 think there can be little doubt that it approximates to that of the preceding species, 

 from which it differs in size and by being more robust comparatively, in having longer 

 eyes, and in the absence of serrature at the base of the posterior angles of the carapace. 



Sestertius, n. gen. 



Carapace large, one-third the length of the animal, anteriorly produced to a small 

 rostrum. 



Pleon slender. 



Telson long, and terminally cleft. 



Ophthalmus broad and short. 



First pair of antennae having a single flagellum. 



Second pair furnished with a broad foliaceous scaphocerite that is rigid on the outer 

 margin. 



The first pair of gnathopoda is long, slender, and terminates in a brush of hairs. 



The first pair of pereiopoda is robust and chelate ; the second is scarcely so robust 

 as the first, and is also chelate ; the third, fourth, and fifth pairs are strong but 

 simple. 



The pleopoda are biramose ; the terminal pair have the branches subequal and well 

 developed as two foliaceous plates. 



Observations. — The remarkable feature of this genus exists in the long and slender 

 gnathopod, which is developed somewhat after the manner of that organ in the Schizopod 

 genus Nematoscelis as described by Sars ; ] for this reason I have thought it desirable to 

 classify it with the aberrant forms rather than with the more normal types of this division. 



Sestertius duplicidentes, n. sp. (PI. LXXXV. fig. 5). 



Carapace dorsally smooth and anteriorly produced to a sharp-pointed rostrum. The 

 pleon is much narrower than the carapace, and each somite except the first is armed with 

 two teeth, one on each side of the median line. 



The telson is nearly as long as the sixth somite and terminally cleft. 



The ophthalmopoda are short and thick. 



The peduncle of the first pair of antennae is subequal with the length of the rostrum, 

 as is also the scaphocerite of the second pair. 



The first pair of gnathopoda is long, slender, and terminates in a few long hairs. 



The first pair of pereiopoda is robust and chelate ; the second is similar but not 

 quite so large ; and the three succeeding ones are simple. 



1 Zool. Chull. Exp., vol. xiii. part xxxvii. p. 126. 



