84 



in front : tentacles widely spread at their base, long, slender, 

 and pointed : eyes small and rather of an oval shape : foot 

 narrow, rounded in front and narrowing gradually behind to 

 a blunt point. 



SHELL flat above, with a depression in the centre, slightly 

 concave below, rather thin, not glossy, greyish-white, closely 

 striate in the line of growth, and more strongly striate or 

 ridged spirally : epidermis thick, sometimes hispid or bristly 

 periphery slightly compressed on each side, but not keeled : 

 whorls 5, the last exceeding the rest in size : suture rather 

 deep : mouth obliquely oval : outer lip slightly reflected ; the 

 upper part projecting considerably : inner lip spread on the 

 columella, but continuous with the outer lip : umbilicus very 

 large, but not deep. L. 0-08. B. 0-275. 



Var. Draparnaldi. Shell more closely and sharply striate 

 in the line of growth : periphery distinctly keeled : umbilicus 

 deeper. P. spirorbis, Drap. Hist. Moll. p. 45, pi. ii. f. 8-10. 

 Helix Draparnaudi, Sheppard, in Linn. Tr. xiv. p. 158. P. 

 Draparnaldi, Jeffr. in Linn. Tr. xvi. p. 386. 



HABITAT : Same as that of the last species, but more 

 generally diffused. The most northern limit in these 

 islands appears to be Aberdeenshire. It is also an upper 

 tertiary fossil. The variety has been found at Holbrook 

 in Suffolk (Sheppard) ; Cardiff, Bristol, and Church 

 Stretton in Shropshire (J. G. J.). It has been referred 

 by the authors of the ' British Mollusca ' to the P. margi- 

 natus of Draparnaud. This common species ranges from 

 Siberia to Portugal and Algeria. 



The spire is often twisted or distorted in this, as well 

 as in the other species of Planorbis. The spiral striae 

 are always visible, even in dead and water-worn speci- 

 mens which have lost their epidermis. The finest spe- 

 cimens I have seen were kindly sent to me by my friend 

 Mr. Norman, who found them at Kibworth, Co. Durham, 

 their diameter being rather more than a third of an 

 inch. 



In all probability this was the Helix spirorbis of Linne*. 



