REPORT ON THE CRUSTACEA MACRURA. 36{> 



Acanthosoma tynitelsoiiis 1 (Fl. LXIV. fig. 2). 



The sjjecimen repi*esented in this figure corresponds in development with that shown 

 in fig. 1 on the same plate. It is probably a slightly older moult of a different but 

 closely allied species. 



The carapace appears to be scarcely half the length of the animal, The rostrum is 

 not quite half the length of the carapace, and is generally free from ornamentation, 

 except for a few points near the apical extremity. The spinous processes are also 

 nearly free from ornamentation, and the smaller dorsal teeth arc cpiite smooth. The 

 lateral processes in a line with the mandibles are strongly serrate, those posterior are 

 smaller and but slightly serrate, and the dorsal one on the posterior median line is 

 slender and almost free from teeth. 



The pleon has the five anterior somites subecpial, and dorsally armed with long- 

 slightly spinous teeth, of which that on the third somite is the longest ; the sixth somite 

 is twice as long as the preceding, and dorsally armed at the posterior margin with a short 

 smooth tooth. 



The telson is short, or less than a third of the length of the outer plate of the rhipidura, 

 and terminates in a wide short fork. 



The ophthalmopoda are about two-thirds the length of the rostrum, and have the 

 eye considerably broader than the stalk. 



The first pair of antennae is longer than the rostrum, and terminates in two short 

 uniarticulate rami. 



The second pair of antennae has the inner branch nmltiarticulate, and the outer, 

 which represents the scaphocerite, nearly three-fourths the length of the inner, scarcely 

 broader, and armed on the outer margin with a tooth that is a considerable distance 

 from the extremity, which, as well as the inner margin, is fringed with hairs that are 

 rather short. 



The oral appendages, as well as those of the pereion, are present, but, especially the 

 latter, in an incipient condition. 



The pleopoda are all developed, and the posterior pair which belongs to the rhipidura 

 is biramose ; they are all feeble organs except the posterior pair, which is long, narrow, 

 and, like that of the preceding species, armed with a tooth about one-third distant 

 from the base, the margin beyond being fringed with hairs. 



Length, 4 mm. (0"16 in.). 



Habitat. — The AVestern Pacific Ocean. 



This specimen is nearly of the same size as the preceding one, but it differs in 

 development in several points. The pleopoda are not yet visible in fig. 1, whereas in this 



1 rvjog, small. 



(ZOOL. CHALL. EXP. PAET LII. lSSG.^ Fff 47 



