JEFFREYSIA. 63 



which resemble tentacles but are close together : tentacles cy- 

 lindrical, rather short, with blunt tips : eyes large, round, and 

 sessile, placed far behind the tentacles : foot lanceolate, short, 

 deeply cloven and bilobed in front, bluntly pointed or almost 

 round behind. 



SHELL globosely conical (like that of Valvata piscinalis), ex- 

 tremely thin, transparent, highly glossy, and partially irides- 

 cent : sculpture the same as in the preceding two species : colour 

 whitish when the shell is empty, dark horncolour when con- 

 taining the animal or its dried remains : spire short and com- 

 pressed ; apex blunt : whorls 3 J, very tumid, rapidly enlarging ; 

 the last occupies three-fourths of the spire : suture remarkably 

 deep : mouth roundish-oval, somewhat detached, half the length 

 of the spire : outer lip sharp and thin, considerably incurved 

 above, slightly expanding and rounded below : inner lip sepa- 

 rated from the pillar to a greater extent than in either of the 

 other species, so as to make the peristome more distinct : 

 umbilicus rather narrow but deep : operculum shorter and 

 more oval compared with that of the other species ; the marks 

 of growth are also more conspicuous, and evidently show a 

 concentric arrangement. L. 0*05. B. 0-065. 



Monstr. Partly scalariform, in consequence of the suture 

 being excavated and becoming much broader near the mouth. 



HABITAT : On Laminaria at Croulin Island, in Skye 

 (Barlee), and, with J. diaphana and /. opalina, at the 

 Whalsey Skerries (Barlee and J. G. J.) ; rather plentiful. 



The tentacular processes of the snout in this species are 

 much smaller and further apart than the true tentacles. 

 In J. opalina the snout is very prominent, and quite 

 distinct from the second pair of tentacles. In both 

 species the hinder tentacles are usually borne at a right 

 angle to the axis of the shell, and the other processes 

 in front diverge at an angle of about 45. 



