HELIX. 207 



called hybrida, there does not appear to be any greater 

 reason for changing Montagu's name than there was in 

 the similar case of H. revelata. 



D. Shell subconical or depressed, and banded: outer lip 

 strengthened by an internal rib : umbilicus large or distinct. 



15. H. PISA'NA*, Muller. 



H. Pisana, Mull. Verm. Hist. pt. ii. p. 60 ; F. & H. iv. p. 56, pi. 

 cxv. f. 7, 8. 



BODY yellowish-grey with a tinge of red in front, rather 

 strongly tubercled : mantle often dark-brown, tinged with 

 yellow and marked with very small and numerous milk-white 

 specks : tentacles rather broad at their base, but slender, 

 finely shagreened ; the so-called optic nerves continue along 

 the neck, so as to form two dark lines ; bulbs very globular 

 and of a reddish colour, indistinctly speckled with brown : 

 foot long, somewhat truncate in front, gradually narrowing 

 and pointed behind, but not keeled. 



SHELL subglobular, slightly compressed above, convex be- 

 low, rather solid and opaque, moderately glossy, yellowish- 

 white, beautifully marked with brown spiral bands, which 

 vary greatly in number (there being sometimes as many as 

 fifteen or sixteen on the last whorl, but usually only one 

 underneath), and more or less marked tranversely with short 

 oblique streaks of the same colour, causing the upper part of 

 the shell to appear speckled; sculpture consisting of irregular 

 striae in the line of growth and of fine, close, spiral striae, 

 which intersect the transverse striae on the upper whorls and 

 give to the surface a delicately reticulated appearance : peri- 

 phery rounded : epidermis extremely thin and only percep- 

 tible under a microscope : whorls 5^, very convex, but com- 

 pressed towards the suture, the last occupying considerably 

 more than one-half of the shell : spire somewhat raised, but 

 having a blunt point, which is of a purplish-brown colour : 

 suture rather slight : mouth forming a segment of two-thirds 

 of a circle ; interior sometimes pink or blush-colour and fur- 

 nished with a slight rib, which is either pale yellowish, 

 white, or pink : outer lip sharp but thickened, reflected in 

 the direction of the umbilicus and especially over it, rather 

 * First found at Pisa. 



