SPH.EROMA. 401 



ISOPODA . SPHMROMID^E. 



NORMALIA. 



GenusSPH^EROMA. (Latreille.) 



Generic character. Animal capable of rolling itself into a 

 ball. Cephalon small, with the eyes dorsally situated at the 

 posterior angles. Antennae small. Pereion much broader than 

 the cephalon, with seven distinct segments, having the first 

 laterally anteriorly produced, so as to reach the anterior mar- 

 gin of the cepbalon. Coxae small. Pleon having all the 

 segments fused together, with the posterior margin entire. 

 Uropoda consisting of a peduncle that is posteriorly produced 

 into a long, flat, oval process, carrying a single ramus which 

 is articulated near the base. 



THE genus, as originally designed by Latreille, was 

 co-extensive with the present family (with the ex- 

 clusion of the remarkable genera, Circeis (Australian), 

 Amphoroidea (Chilian), Cassidina and Ancinus (both of 

 unknown locality), four genera recently established by 

 Professor Milne Edwards. Dr. Leach, however, in his 

 Memoir in the " Dictionnaire des Sciences Naturelles," 

 divided it into seven genera, most of which have sub- 

 sequently been adopted by Latreille and other carcino- 

 logists ; the typical genus Sphaeroma comprising most 

 of those species which are able to roll themselves up 

 into a ball, at which time the lateral appendages of the 

 tail are not visible. 



These animals are of small size, rarely reaching to the 

 length of half an inch. 



VOL. II. D D 



