PROPILIDIUM. 253 



also mention that Mr. Dawson dredged several speci- 

 mens in the Moray Firth, but in apparently a semi- 

 fossilized state. L. caeca occurs in the Red and Coral- 

 line Crag ; Uddevalla (Lyell) ; Christiania district, in 

 the older portion of the post-pliocene or glacial forma- 

 tion, 400-440 ft. (Sars) ; Antwerp Crag (coll. Nyst) . It 

 inhabits the Arctic and North Seas, from Spitzbergen 

 (Goodsir) and sea of Okhotsk (Middendorff) to Gotten- 

 burgh (Malm), as well as the eastern and western 

 coasts of North America (Couthouy, Stimpson, Bell, 

 and P. Carpenter) ; the depths in these localities vary 

 from 20 to 100 f. 



According to Loven its dentition agrees with that 

 of Tectura fulva. 



The present species is the P. Candida of Couthouy 

 and P. cerea of Moller. 



Genus V. PRO'PILI'DIUM *, Forbes and Hanley. 

 PL VI. f. 1. 



BODY compressed 1 : mantle finely ciliated at its edge: tentacles 

 rather long and slender : eyes wanting : gills, according to 

 Forbes and Hanley, apparently forming two short triangular 

 plumes, which are furnished with large cilia : foot thick. 



SHELL conical and much raised, cancellated, having in all 

 states of growth a minute spiral apex, which is inflected to- 

 wards the rear ; crown central : inside furnished in the middle 

 with a shelf-like triangular plate, which covers about one-half 

 of the crown: central scar indistinct: pallial scar situate 

 within the margin. 



A singular genus, agreeing with Lepeta in the retro- 

 gressive inclination of the beak, but differing from that 

 and every other genus of the Patella family in always 



* From its affinity to the genus Pilidium proposed by the same 

 authors. 



