South African Crustacea. 27 



POLYCHELES NANUS (Smith). 



1884. Pentacheles nanus, S. I. Smith, Ann. Rep. U.S. Fish. Comm., 



1882, p. 359. 

 1886. Pentacheles nanus, S. I. Smith, Ann. Eep. U.S. Fish. Comm., 



1885, p. 651 (47), pi. 7, figs. 1, la, 

 1895. Polycheles nanus, Faxon, Mem. Mus. Comp. Zool. Harvard, 



vol. xviii., p. 121, pi. 33, figs. 1, la, Ib. 



On the middle line of the carapace, hetween the rostral spines 

 and the cervical sulcus, there are two single spines one behind the 

 other, then a pair followed by two others in single file, whereas in 

 Professor Smith's specimen there was only one spine behind the 

 pair. The dorsal part of the fifth pleon segment is unfortunately 

 missing, but the fact of its loss is an indirect testimony to its 

 original prominence. In other respects the pleon agrees with the 

 original description, which is as follows : " The pleon is more 

 deeply sculptured than in P. sculptus, and the dorsal carina very 

 much higher, the recurved carinal teeth of the third, fourth, and 

 fifth somites are very much longer and more slender, and reach far 

 over the somites in front. The edges of the sulcated carina on the 

 sixth somite, instead of being low and uniform, as in P. sculptus, are 

 very high and broken into several prominent teeth on each side, 

 with a stouter and higher tooth at the posterior end of the sulcus." 

 The edges of the side-plates and the median elevation on the telson 

 with its smaller secondary prominence also agree with Professor 

 Smith's account. 



According to Faxon, the fifth peraeopods are chelate in both sexes ; 

 the pleurobranchise four, one on each of the second to the fifth 

 peraeopods, the arthrobranchiae eight, two to each of the first 

 to the fourth perasopods, which also have each a podobranchia ; 

 the third maxilliped has a very minute epipod, and the first to 

 the fourth peraeopods have rudimentary epipods, represented 

 by a plate-like expansion of the base of the stem of the 

 podobranchia. 



The single South African specimen is a female, as evidenced by 

 the sexual openings at the base of the third peraeopods. Adherent 

 to various parts of the body were several small oval eggs, but 

 whether actually belonging to the specimen was not quite 

 evident. 



Length of specimen 65 mm., the carapace being 30 mm. long, 

 and at the cervical groove 22 mm. broad, the pleon 35 mm. 

 long. 



