PACHTSTOMA. 227 



OXTANASPIS. Darwin. Cirripedes. Lepad^, P. 133. PI. iii. 

 fig. 1. A genus of Pedunculated Cirripedes, tlie shells of whicli 

 are thus described, " Valves 5, approximate ; scuta with their 

 umbones in the middle of the occludent margin ; carina rect~ 

 angularly bent, extending up between the terga, with the basal 

 end simply concave." 



OXTSTOMATA. Bl. The fifth family of Asiphonbranchiata, 

 Bl. This family appears to have been formed for the express 

 purpose of providing a place in the system for the genus Jan- 

 thina, which seems to bear so little analogy with other genera 

 of MoUusca, that conchological writers have been puzzled to 

 know where to place it. 



PACHYBATHEON. Gaskoin. A genus established for the 

 reception of a singular small shell resembling MargineUa, but 

 having the columellar lip spread over the body whorl, and the 

 teeth continued across it in folds, giving the front of the shell 

 the appearance of a Cypraea. I think MargineUa Kieneriana, 

 Petit. Sowerby's 'Thesaurus ConchyHorum, PI. Ixxviii. fig. 198, 

 199, 200, will be found to approach this shell, and almost lead 

 it into the Marginellae. Fx. P. Marginelloides. Gaskoin. "West 

 Indies. PI. xxviii. fig. 600. 

 -PACHYLABEA. Sw. Pachystoma, Guild. A sub-genus of 

 Ampullaria, the outer lip of which is thickened within. Ex, 

 Ampullaria globosa. 



PACHYMYA. Sow. (Traxve, pachus, thick, and Mi/a.) Fam. 

 Cardiacea ? Lam. — Bescr. Obliquely elongated, equivalve, thick 

 sub-bilobed, with beaks near the anterior extremity ; ligament 

 partly immersed attached to prominent fulcra. — Obs. This 

 singular fossil is shaped like Modiola, but the shell being 

 extremely thick, and the ligament attached to a prominent 

 fulcrum, it is difficult to know where to place it. Pachyma 

 Gigas. PL vii. fig. 130. 



PAGHYSTOMA. Guild, (jraxvQ, pachus, thick ; trrofia, stoma, 

 mouth.) A genus composed of such species of Ampullaria, 

 Auct. as have the edge of the aperture thickened and grooved 



Q 2 



