240 



THE VOYAGE OF H.M.S. CHALLENGER. 



pereiopoda are scarcely so far advanced, and the animal as a whole does not appear so 

 mature in form, although the pleopoda are more advanced. 



This specimen, together with one taken on the 20th of April, 1876, corresponds very 

 closely with that shown on PI. XL VI. fig. 1, which differs in having a small cusp behind 

 the one on the dorsal base of the rostrum, in having the pleopoda more advanced in 

 development, and in having the lateral plates of the rhipidura longer than the telson. 



The following is the description of another specimen (fig. 46) taken at the surface on 

 February 5, 1875, near Mindanao, Saniboangan, Philippines, associated with Leucifer, 

 and with the young of Alphseus and Penseus. 



Length, 6 mm. (0 - 25 in.). 



Carapace one-third the length of the animal, produced anteriorly to a smooth rostrum, 

 nearly as long as the carapace, and flanked on each side of the base with a strong 

 ophthalmic tooth ; dorsally furnished on the postgastric region with a small tubercle (or 

 the remains of a broken tooth), and armed on each side of the median line of the 



Fig. 46. — Young of a species of Aristeus (?). 



posterior margin with a long, straight, spine-like tooth ; the lateral margin consists 

 of a rigid, longitudinal border, commencing in the outer antenna! tooth, and terminating 

 posteriorly in two small marginal points or teeth. 



The first somite of the pleon is dorsally smooth, furnished laterally with a pleocleis or 

 small tooth that is directed anteriorly, and overlies the posterior margin of the carapace. 

 The second somite is dorsally armed near the posterior margin with a strong tooth that 

 is more than half the length of the animal. 



The third somite is also furnished with a dorsal tooth, short and strong, the two 

 next with a tooth still shorter, and the infero-lateral margin is jiroduced to a long tooth. 

 The sixth somite is nearly equal in length to the three preceding, subcylindrical, and 

 armed posteriorly with a dorsal tooth and one on each side at the postero-lateral angle. 

 The telson is short and posteriorly produced at each angle to a small tooth. 



