Messrs. H. and A. Adams on two new genera of Mollusca, 63 



agrees with the P. sublcevis (M'Coy) of the Irish Silurian rocks, 

 but from which it is distinguished by its fine clo««.^t"f]^«°- . , 

 Common in the Ui)per Ludlow shale of Cwm Craig Ddu ; Mid- 

 dleton Park near Sedburgh; Erw Gnifach and m the Ludlow 

 schists above Parklane; Upper Ludlow rock of Benson Knot, 

 Kendal, Westmoreland ; also in the sandy schists of Pont-ar-y- 



Uechan. 



{Col. University of Cambridge.) 



VIL — On two new genera of Mollusca. 

 By Henry and Arthur Adams, Esqrs. 



To the Editors of the Annals of Natural History. 



19 Hanover Villas, Kensington Park, 

 Gentlemen, Dec. 17, 1850. 



Should vou consider the following notice of two apparently new 

 genera of Mollusca worthy of insertion in the ' Annals, you wdl 

 obliare us by its publication. , -,. , 



We remain. Gentlemen, your very obedient servants, 



H. & A. Adams. 



Genus Paxillus, nobis. 

 Gen Char. Shell pupiform, rimate; spire acuminated ; aper- 

 ture semiovate, ascending on the body-whorl; inner lip adnate, 

 spreading, flexuous; columella with a single promment tooth- 

 like plait • outer lip with a double peritreme, emarginate ante- 

 riorly; umbilical region with a spiral, elevated ridge, terminating 

 in a notch at the fore part of the aperture. 



Paxillus adversus, nobis. 

 P testa ovato-acuminata, sinistrali, rimata, spira acuminata, cor- 



neo-fusca, semipellucida, longitudinaliter substriata. 



Hab. Singapore, on mud-banks, in company with Truncatella 

 and Melampus. Dr. Livesay. 



Obs This curious little genus, lately brought to this country 

 by Dr Livesay, Surgeon of H.M.S. Albatross, seems to approx- 

 imate to Diplommatina of Benson, which, having sessile eyes on 

 the base of the tentacles, and an operculum, belongs to the 

 family Truncatellidce. There is, however, no indication of oper- 

 culum in Paxillus, and the plait on the columella would render 

 it referable to the family Auriculidce, with which group we place 

 it until, at least, more information is obtained concerning it. 



