3<30 THE VOYAGE OF H.M.S. CHALLENGER. 



the arrangement of the spines on the posterior dorsal process of the carapace, are probably 

 due to the more or less perfect display of the specimen ; but there is one structurally 

 important part that is essentially different, and demonstrates the specimen to be of a 

 younger stage. For, in our figure of the next stage, as well as in that given by Claus, the 

 two large spinous processes on the frontal margin, one on each side of the rostrum, are 

 projected forwards on a process of the carapace, and the ophthalmopoda are implanted 

 behind them, whereas in the figure given by Suhm the frontal spinous processes are 

 represented as being external and posterior to the ophthalmopoda, and the frontal 

 margin of the carapace does not project ; an evidence of its younger condition. 



The next stage we know is that given on PL LXII. of this Report, and agrees 

 closely with that figured by Clans, which represents the ventral surface, whereas ours 

 gives the dorsal, but the appendages are shown through the transparent integument so as 

 to indicate their relative positions. 



It is difficult to believe that this is a further development of the same animal, inas- 

 much as there are two large spinous processes thrown out at the base of the rostrum and 

 anterior to the ophthalmopoda. Our specimen has two spines less on the telson than are 

 given in Claus's figure, but in all other details they resemble each other, and are probably 

 the young of very closely allied species. 



The carapace is nearly circular, with the cephalic region considerably advanced and 

 projecting forwards, and furnished with a central spinous rostrum and two lateral spinous 

 processes. The rostrum is about half the length of the carapace and armed with two 

 lateral spines opposite each other and directed obliquely forwards, and two on the upper 

 surface, in a line one before the other. The lateral spinous processes at the base of the 

 cephalic lobe much resemble those at the lateral margin, and arc directed obliquely 

 forwards, and covered with long spines pointing in every direction ; I counted fourteen 

 or fifteen on each. The depression formed between the base of these processes and the 

 anterolateral margin of the carapace, forms the orbital notch in which tin 1 ophthal- 

 mopod is situated. The lateral spinous processes are opposite each other in a line 

 posterior to the mandibles, each is armed with very long spines, of which I counted 

 fifteen, the one at the apex carrying a small hook at its side, somewhat distant from its 

 apex, and three at the base are on the dorsal surface. The posterior spinous process is 

 long, straight and slender, and reaches beyond the extremity of the telson ; it is armed 

 with eight long spines, two of which at the base on each side are directed obliquely 

 upwards and forwards ; two a little posterior pass laterally outwards, two on the 

 under side, still more posteriorly, are directed obliquely downwards and forwards, and 

 two from near the same point of origin are directed obliquely downwards and backwards. 



The pleon is armed on each side of the posterior margins of the five anterior somites, 

 with a long spinedike tooth passing outwards and probably downwards. The telson is 



