RISSOA. 133 



The shape of this shell, which is not particularly thin, 

 considering its minuteness, is globular-conoid ; its texture 

 is transparent ; its surface of an uniform clear pale fulvous 

 yellow, perfectly smooth, always shining, and at times 

 iridescent. There are four gently, or but moderately 

 shelving convex volutions, that rather quickly increase in 

 length, and are divided by a profoundly impressed, and 

 almost horizontal, suture, beneath which they appear 

 marginated, but are not so in reality, the apparent line 

 being merely the termination of the preceding volution, 

 which, through the pellucidity of the shell is rendered 

 visible to us. Fully one half of the entire length is 

 occupied by the body-whorl, which is swollen, peculiarly 

 broad, and well rounded but abrupt at its basal declina- 

 tion; the spire itself is short, and tapers quickly to a 

 very obtuse apex; the axis is sub-perforated. The mouth 

 is moderate as to size, is equal in length to the portion 

 above it, and is of a broadly ovate form, being contracted 

 above, and well rounded below. The outer lip, whose 

 chief projection is towards the base of the shell, is simple, 

 acute, and peculiarly and almost equally arcuated both 

 above and below. The peristome is continuous, the parietal 

 enamel of the left lip being very distinctly perceptible. 

 The general inclination of the inner lip is obliquely 

 subrectilinear ; hence the aperture, with the subumbilicus 

 behind the broadly reflected pillar-lip, reminds one of the 

 genus Natica. Three quarters of a line is about the 

 general length of the individuals we have examined ; their 

 breadth is a trifle less. 



Discovered on the shore at Weymouth by Mr. Metcalfe. 



If this be the Helix litorina of Delia Chiaje, Trwn- 

 catella littorina of Philippi, taken at Palermo, its po- 

 sition in the genus Bissoa is extremely questionable. 



