REPORT ON THE CRUSTACEA JVIACRURA. 245 



longitudinally, and project anteriorly so that their extremity reaches as far forwards as 

 the hase of the penultimate pair of pereiopoda. 



In the male specimen from Fiji the petasma corresponds precisely with that of the 

 male taken at the Mauritius, and now in the Museum of the Jardfn des Plantes. 



Penseus canaliculatus, var. japonicus (Pis. XXXI. , XXXII. fig. 4, XXXVII. fig, 2). 



Penxus canaliculatus, de Haan, Crust, in v. Siebold, Fauna Japonica, p. 190. 



This variety differs from Milne-Edwards's typical specimen and description of Penseus 

 canaliculatus in having the telson terminating more acutely, and in having three small 

 spines on each lateral margin, but more especially in the peculiar formation of the comple- 

 mentary external female apparatus which I propose to call thelycum. 



Length (female), 175 mm. (7 in.). There is no male of this variety in the collection. 



Habitat. — Japan. 



The carapace has a central, narrow, longitudinal groove extending from the posterior 

 extremity of the rostral carina to near the posterior margin of the carapace, and on each 

 side another that extends from the anterior extremity of the rostrum to the posterior 

 margin of the carapace. The rostrum is about, half the length of the carapace, the dorsal 

 crest, reaching posteriorly to nearly the middle of the carapace, is armed with nine teeth 

 interspersed with fine hairs, and with one tooth on the under surface, situated immediately 

 beneath the anterior rostral tooth. The two posterior somites of the pleon are laterally 

 compressed, forming an acute dorsal angle that is produced to a small tooth at the 

 posterior extremity of the sixth somite. The telson is centrally grooved with a longi- 

 tudinal furrow that reaches from the anterior margin to the posterior extremity, and 

 is armed with three small spines on the lateral margin. 



The eyes (PL XXXI. a) are large and ovate, with the inner side flattened and the 

 outer rounded, projecting on a biarticulate peduncle, and reaching as far anteriorly as the 

 tooth on the inferior margin of the rostrum. 



The first pair of antenna? (b) has the peduncle reaching as far as the apex of the 

 rostrum; the first joint is long, wide, and scale-like; the inner margin is longitudinally 

 straight, deepest posteriorly, where it is furnished on the inner side, near the base, 

 with a long slender prosartema copiously fringed with hairs, and thinning anteriorly ; on 

 the outer side it is armed at the extremity with a sharp-pointed tooth, and a styl<>- 

 cerite lying closely against the side and directed forwards (not shown in the figure); the 

 upper margin is longitudinally curved, and fringed with a linear row of delicate cilia, 

 the lower is nearly straight ; the outer and inner margins of the joint are subparallel, 

 slightly approximating at their anterior extremity ; the surface between the two lateral 

 margins is deeply excavate, especially towards the base, where the auditory apparatus 



