203 LAMELLARIIDTK. 



Genus CRYPTOCELLA, H. and A.Adams. 



? Mantle depressed, subvervucose or smooth, anterior 

 fold median. 



Shell thin, pellucid, calcareous; spire small; aperture 

 very large, patulous; inner lip receding. 



Sy7i. Lamellaria, sp. Mont. 



Ex. C. latens, Milller, pi. 21, fig. 4, 4, a. Shell, 

 C. tentaculata, Montagu, fig. 4, 6. 



This form differs from Lamellaria in the back not 

 being tubercled, and in the position of the eyes ; it has 

 not the fissure on the back described as peculiar to M. 

 prodita by Dr. Loven. The shell is more calcareous 

 than that of Lamellaria. 



Species of Cryptocella. 

 latens, Midi. tentaculata, Mont. 



Genus MARSENINA, Gray. 



Teeth, central (1), lateral (3 3), hooked, equal. > Mantle 

 depressed, very thin or fissured on the back, subverrucose ; 

 anterior fold subsinistral, and the lateral canal dextral. 



Shell elongated, opaque; spire minute; outer lip some- 

 what straight. 



Si/n. Lamellaria, sp. Loven. 



Ex. M.' prodita, Loven. 



This genus differs from the others of the family in the 

 mantle (? operculigerous lobe) being fissured down the 

 back. 



