REPORT ON THE CRUSTACEA MA CRURA. 



381 



specimen given in tig. 5, but is entirely wanting in that from which fig. G is taken, and 

 the fourth (») and fifth (o) pairs of pereiopoda are here in a .stage of gemmation, whereas 

 in tig. 4 they arc not appreciable. 



Length. 4 mm. (0T7 in.). 



Habitat. — The Pacific Ocean ; taken .March 15, 1875, about 5° north of New Guinea. 



Mastigopus crassus, n. sp. (Suhm, MS.). 

 " Sergestes (" crassus '). 



" Larval stage previous to the moulting of the mature animal. 



Fig. 52. — (IV) Mastigopus crassus. In. labrum ; mdb, mandible; tax 1 , first maxilla; rax 1 , second maxilla; mxp, 

 maxilliped ; g\ first gnathopod ; : i-, second gnathopod ; p 1 , first pereiopod ; p-, second pereiopod : p\ third pereiopod ; 

 p 4 ' 4 , fourth and fifth pereiopoda. 



"The posterior two pereiopoda are only rudimentary, and the animal now morpho- 

 logically resembles a Leucifer, 



