362 THE VOYAGE OP H.M.S. CHALLENGER. 



considerably advanced in development, and are with the second pair of antennae the 

 only appendages that demonstrate the Zoea to be of Macrurous origin. They consist 

 of a short basal joint and two unequally long, membranous branches directed outwards, 

 downwards and forwards, and implanted at a distance from the terminal portion of the 

 forked telson, which is not defined from the preceding somite. 



Length, 2 mm. (0-08 in.). 



Habitat— South Atlantic, March 1 to 4, 1876 ; lat. 32° S., long. 45° W.; between 

 Monte Video and Tristan da Cunha. 



This is as far as we are able to trace the changes in the Elaphocaris of the same or of 

 closely allied species. 



Elapliocaris crassus, Willemoes Suhm, MS. (PL LXI. fig. 4). 



This is another specimen which has been found in the Pacific. It differs in form in 

 certain parts, particularly in the character of the spiny processes, which appear to show 

 that it belongs to another, but in all probability more or less closely allied genus. 



The carapace dorsally is nearly circular ; the anterior central extremity is produced 

 to a long rostrum, about two-thirds the length of the carapace ; it is straight and tapers 

 to a point, having the margins fringed with short sharp spinules. On each side of the 

 base of the rostrum there is a long, curved, anteriorly-directed, spinous process, smooth 

 on the inner side and armed on the outer with six long spines. The lateral spinous pro- 

 cesses consist of one long central spine, armed towards the apex with small denticulations, 

 while near the base there stand two anterior and three posterior long, blunt, and rather 

 flexible spines. On the posterior margin of the carapace on each side of the pleon is a 

 broad lobe or tubercle crowned with five or six long, blunt-pointed, finger-like, subflexible 

 spines, but in the median line there is no spinous process as in other species. 



The pereion in this specimen is developed and exposed posteriorly to the carapace. 



The pleon has the five anterior somites subequal, and armed on each side with a 

 long, slender, sharp spine. 



The telson is large, bilobed, and armed with seven very long semiflexible spines. 

 The most anterior is the smallest and most slender, and stands on each side not far from 

 the posterior pair of pleopoda. The five succeeding are very long, flexible, and slender, 

 and beyond these on the inner side is the last, that points diagonally backwards and 

 inwards. 



The ophthaknopoda are fungiform, the ophthalmus being much broader than the stalk. 



The first pair of antennas (6) is single-branched, four-jointed, and free from hairs, 

 except the terminal joint, which is tipped with two long hairs and subapically with two 

 short ones. 



