180 CRUSTACEA. 



length of the eyes ; the first joint is entirely situated under the ocular 

 cavities. 



If there are seven segments in the tail of both sexes, we have the 

 genus Parthenopc properly so called * of Leach. 



If that of the males presents but five, it is his genus Lambrus f- 



The lateral antennae of the others are sensibly longer than the eyes ; 

 their first joint extends to the superior internal extremity of the 

 cavities peculiar to these latter organs, and appears to be confound- 

 ed with the shell. The post-abdomen is always composed of seven 

 segments. The claws of the females are much shorter than those of 

 the opposite sex. The same naturalist distinguishes these Crustacea 

 generically by the name of Eurynoma. But a single species is known 

 which inhabits the English and French coasts {. 



All the other Parthenopes, one excepted, are from the Indian 

 Ocean. 



In the following ones, the claws always project, and their length, at 

 most, is double that of the body ; their fingers are not suddenly bent 

 into an angle ||. 



Here the length of the longest feet the second barely exceeds 

 that of the shell from the eyes to the origin of the tail. The under 

 part of the tarsi is usually either dentated or spiny, or furnished with 

 a ciliated fringe terminated like a club. 



We will commence with those whose ocular pedicles are very short, 

 or of a mean length, susceptible of being entirely retracted within 

 their cavities, and whose claws, at least in the males, are considerably 

 thicker than the other feet. 



MITHRAX, Leach. 



Robust claws ; ends of the fingers like the bowl of a spoon ; stem 

 of the lateral antennae sensibly shorter than the pedicle ; the tail 

 composed of seven segments in both sexes. 



All the known species are from the American seas If. 

 i 



ACANTHONYX, Latr. 



A tooth or spiniform projection on the inferior side of the tibiae ; 

 under part of the tarsi pilose, and as if pectinated ; superior surface 



* Parthen. horrida,Fab.; Rumph., Mus., IX, 1 ; Seba, III, xix, 16, 17 ; Herbst , 

 XIV, 88. 



f Panth. lonyimana, Fab.; Rumph., Mus., VIII ; P.giraffa, Fab.; Herbst., 

 XIX, 108, 109; P. lar, Fab. ; P. minis, Latr. ; Cancer contrarius, Herbst., Ix, 

 3; P.macrochelcs, Lat., Herbst., XIX, 107; Cancel' longimamts, L., fern., P. 

 trigonomana, Lat. ; Cancer prensor, Herbst., xli, 3. 



J Cancer asper, Peon., Brit. Zool., IV ; Eurynoma aspera, Leach, Malac. Brit., 

 XVII. 



Parthenope angulifrons, Latr.,Encyc. Method. ; Cancer longimamts, Olivi. 



|| The first joint of the lateral antennae appearing to form part of the shell, has 

 been mistaken by several naturalists, the second having been considered by them 

 as the first. 



^f Mithrax spinicinctus, Latr.; Desmar., Consid., p. 150; Cancer, hixpidus, 

 Herbst., XVIII, 100 ; Cancer acukatus, Herbst., XIX, 104 ; C. spinipes, ejusd., 

 XVII, 94. The laclnts hircvs, Fab., is perhaps a congener. 



