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



with four compound spinous processes. The anterior forms the rostrum and is about as 

 long as the carapace, and supports on each side and along the dorsal surface a series of 

 about nine or ten long, straight, spine-like processes, besides two or three small teeth 

 at the extremity. Two, one on each side, spring from the lateral surface in a 

 line slightly posterior to the mandibles ; these also carry seven or eight long, straight, 

 spine-like processes; the fourth is produced posteriorly as a long, straight, spinous process 

 directed backwards, and is armed with four long spines, two on each side near the base, the 

 anterior pair directed outwards, upwards, and backwards, and the posterior horizontally 

 outwards. 



The pleon does not project posteriorly beyond the carapace for more than half the 

 length of the latter, and it carries no appendage. 



The telson is widely forked, each ramus being broad, flat, and armed with four long 

 and two short spines. On the outer and anterior side of the base of the telson there 

 is on each side one strong, straight tooth of moderate length, and on the distal extremity 

 of each ramus are four very long spinedike processes, the posterior three terminally 

 serrate, that appear to be flexible in character, and on the inner side, pointing diagonally 

 towards each other, is another short curved tooth or spine. 



The ophthalmopoda are well developed, pedunculated, pyriform and robust, the 

 ophthalmias being slightly larger than the distal extremity of the stalk. They stand on an 

 advanced projection of the cephalon that forms the base of the great rostral process, 

 and their length is about one-third that of the carapace. 



The first pair of antennas is four-jointed ; the terminal joint, which represents the 

 future flagellum, is narrower than the preceding one, of about the same length as the 

 third joint, and terminates in three long, slender hairs. 



The second pair of antennas is biramose ; the inner branch, which is nearly as long as 

 the peduncle of the first pair, is smooth on one side and fringed with hairs on the other, 

 ainl homologous to the scaphocerite ; the outer branch is three-jointed and homologous 

 to the two terminal joints of the peduncle and rudimentary flagellum. 



The epistoma is armed with a long, straight, spine-like process which reaches as far 

 forwards as the origin of the ophthalmopoda. 



The mandibles consist of two large, robust organs, that even at this stage approach 

 in appearance those of the adult; behind these there are probably two pairs of appen- 

 dages, but I have not been able to determine them with certainty. 



The pereiopoda are not yet visible even as buds. 



The organism as it now appears is that of an early Zoea — 1 say early, because the 

 gnathopoda are not yet discernible at this stage. 



The next stage, but of which there is no specimen iu the Challenger collection, is one 

 closely resembling the last, and is figured by Claus in his Crustaceen System (Tab. v. 



