352 ESCHARID^E. 



the cell rises markedly towards the mouth, and the front 

 of the peristome is thus elevated, while the upper mar- 

 gin appears depressed. In S. cheilostoma the surface is 

 level and uniform, and the margin as much elevated above 

 as in front. That species is always destitute of avicularia ; 

 whilst in S. marmorea there is usually one below the 

 orifice, occupying much the same position as in S. reticu- 

 lata. There are also differences in the denticle on the 

 lower margin, which in the present species assumes the form 

 of a very broad plate. S. marmorea, so far as I know, is 

 destitute of the deep-red colour which is so characteristic 

 of its ally. 



Apart from these divergences, which in the aggregate 

 are not unimportant, there is a difference in general ap- 

 pearance which can hardly be formulated. 



I have only seen a few specimens of 8. marmorea ; and 

 possibly a larger series might show an intermingling of 

 characters ; but at present I hold the two forms to be 

 distinct. 



SMITTIA BELLA, Busk. 

 Plate XLII. figs. 9, 10. 



LEPRAUA BELLA, Busk, Quart. Journ. Micr. So. viii. (I860), 144, pi. xxvii. 

 fig. 2 (not L. bella, Norman, Shetland Polyz., Rep. Brit. 

 Assoc. 1868, 306, which is a var. of Porella concinna). 



Zocecia ovate, punctured ; aperture orbicular, with a spout- 

 like sinus below, and within it a large bifid denticle ; 

 peristome raised, often thickened. Ocecia subglobose, 

 punctured. 



HABITAT. On shells. 



LOCALITY. Shetland (Barlee). 



