DECAPODA. 187 



The others, such as the C. voute — Cancer calappa, L. ; Ca- 

 lappa fornicata. Fab.; Herbst., XII, 73, 74, have the marginal 

 dilatations of the shell entire. This species inhabits the seas in the 

 vicinity of Australia and the Moluccas. 



^THRA, Leach. 



The .^thrae differ from the Calappae in their very flat shell, in their 

 forceps, which are not raised perpendicularly, and which do not 

 overshadow the forepart of their body, and in the almost square form 

 of tlie third joint of the external foot-jaws. 



Sometimes* the shell is a transversal oval, and at othersf forms 

 a short and very wide triangle laterally dilated and rounded. The 

 claws arc but slightly elongated, and are tolerably thick; here they 

 are longer, angular, and remind us, as does also the form of the shell, 

 of the Parthenopes. These latter species might constitute a separate 

 subgenus. 



Finally, our last and seventh division, that of the Notopoda, con- 

 sists of Brachyura, whose last four or two feet are inserted above 

 the level of the others, or which appear to be dorsal and look upwards. 

 In tliosc where they terminate by a sharp hook, they are visually 

 employed by the animal in seizing various bodies, such as shells, 

 Alcyonii, &c., with Avhich it covers itself. The tail consists of seven 

 segments in both sexes. 



The tail of some of them, as in other Brachyura, is folded under, 

 and their feet terminate in a sharp hook and are not fitted for 

 natation. 



Here the shell is nearly square, and terminates anteriorly in an 

 advancing and dentated point, or it is sub-ovoid or truncated before. 

 In the 



Homola, Leach, 



I'he eyes arc supported by long pedicles closely approximated at 

 the base, and inserted under the middle of the front. The two posterior 

 feet are alone turned up. The claws are larger in the males than in 

 the females. 



The shell is extremely spinous, with a dentated projection on the 

 middle of the front. The superior foot-jaws are elongated and 

 salient. 



These Crustacea inhabit the Mediterranean, and were designated 

 by Aldrovandus under the name of Hippocarcini ; they are the Thel- 

 xiopes of Rafinesque. Some of the species attain a great size t. 



DoRipPE, Fab. 



The eyes widely separated and placed at the anterior and lateral 

 angles of the shell ; the four posterior feet turned up ; the claws short 



* Aithra depressa, Lam., Hist, des Anim. sans Verteb. ; Cancer scruposus, L. ; 

 Cancer polynome, Herbst., liii, 4, 5; Desmar., Consid., X, 2. 



t Parfhenope fornicala, Fab. 



X Homola spinifrons, Leach, ZooL Misc., Ixxxviii; Cancer spinifrons, Fab. See 

 the article Homole, Nouv. Diet. d'Hist. Nat. Ed. II, and Desmar., Consider., 

 XVIII, 1. The Dorippe Cuvieri, Risso, belongs to this subgenus. 



