GENUS— P.ECiLASMA. 99 



distinct of any in the genns, and Mr. Gray has proposed 

 to separate it under the name of Dosima ; but consider- 

 ing the close similarity of the whole organisation of the 

 internal parts, together with the transitional characters 

 afforded by L. austraiis, I think the grounds for this 

 separation are not quite sufficient. I have remarked, 

 under L. austraiis, on the affinity between that and 

 the present species. In the carina terminating in a disc 

 (though here not imbedded), there is some slight affinity 

 to Pcecilasma eburnea and crassa, and markedly so in the 

 arrangement of the bristles on the posterior cirri. In 

 the valves being covered with villose membrane, and to a 

 certain extent in the form of the carina and of the occlu- 

 dent margin of the terga, and especially in the two rows 

 of cement -orifices in the peduncle, there is some affinity 

 to Scalpellum. 



PtEcilasma. Nov. Genus* Plate II. 



Anatifa. /. E. Gray. Proc. Zoolog. Soc, 1848, p. 44. 

 Trilasmis. Hinds. Voyage of the Sulphur. Mollusca, 1844. 



Valva, 3, 5, aid 7, approximates: carina solum ad 



basales apices tergorum externa, termino basali aid 



truncato aid in discum j^ofunde infossum producto : 



scuta pcene ovalia, umbonibus ad angidum rostralem 



positis. 



Valves, 3, 5, or 7, approximate : carina extending only 

 to the basal points of the terga ; with its lower end 

 either truncated or produced into a deeply imbedded 

 disc. Scuta nearly oval, with their umbones at the 

 rostral angle. 



Mandibles with four teeth ; maxillae notched, with the 

 lower part of edge prominent; anterior ramus of the 



* noKiAoo-, various, and tkaafia, plate or valve. I have not been able to 

 adopt Mr. Hinds' name for this genus, as it would be too glaringly incorrect 

 to call a five-valved species, a Trilasmis. 



