124 LITTOKIMDiB. 



its inner margin : the parietal enamel is usually profuse 

 in adult examples. A sixth of an inch for the length, 

 and a line or rather more than a line for the breadth, 

 are the ordinary proportions. 



The variety termed grapliica by Turton, is rather 

 stronger than usual, and has its zones much more fiuntly 

 displayed. It is not uncommon at Weymouth, under 

 stones near the old castle, &c., (S. 11.). 



In typical specimens of the aberrant form rupestris, the 

 shell is nearly of an uniform white, and the spiral stripe 

 are obsolete above the angulated commencement of the 

 basal slope. The seeming subsutural line is not impressed, 

 but is merely the overlapped base of the preceding turn 

 revealed by tlic more than ordinary transparency of the 

 shell. 



The animal is of a yellowish white, sometimes (in the 



normal form) slightly tawny, sometimes (in var. ru- 



pestris) more of a milky hue. The snout is prominent, 



narrow, and translucent, showing the jaws and tongue 



shining through ; the tentacles are very long and linear, 



bearing the conspicuous black eyes on their opaque white 



bulging bases. The foot is narrow and oblong, angled, 



but not sharply, in front, obtusely pointed behind. The 



caudal cirrhus, if present, is small ; we have not been able 



to see it. When the creature is at rest the foot is much 



contracted, and the tentacles are turned back on the shell. 



When in motion it moves its tentacles in a waving manner 



alternately ; a habit common to other species of the genus. 



Rlssoa cingillus is strictly a littoral animal, abounding 



between tide-marks in muddy, rocky, and stony places 



almost everywhere around the shores of Britain and 



Ireland. The variety grap>hicus is scarce ; it occurs at 



Langland, near Swansea (Jeffreys). The form riqjestris 



