WATSON: ANATOMY OF HELICAEION. 97 



Helicarion cryptophallus, n.sp. 



Nairobi (?), British East Africa. 



PLATE IV. 



Shell depressed - globose, paucispiral, narrowly rimate, 

 yellowish-green, glossy, translucent, and extremely thin, the 

 greater part of the shell being almost membranous and quite 

 flexible when moist. Spire a little raised ; apex rounded. Whorls 

 2f, rapidly increasing, rounded at the periphery. Protoconch 

 composed of 1^ whorls, spirally punctate, that is to say, 

 ornamented with spiral rows of minute circular depressions. 

 Eemaining whorls almost smooth, excepting for the ill-defined 

 lines of growth, though showing traces of very minute spiral 

 striae when viewed through the microscope. Periostracum of last 

 whorl not always reaching quite to the suture, but leaving next to 

 it a very narrow lighter band. Suture shallow, not describing 

 a regular spiral, owing to the fact that the top of the first half of 

 the last whorl overlaps the spire to a slightly greater extent than 

 does the top of the penultimate whorl, so that the jDrotoconch has 

 the appearance of being slightly tilted to the left. Aperture trans- 

 versely oval, about 7"5 mm. broad. Peristome simple, very thin, 

 slightly reflected over a narrow rima at its junction with the 

 penultimate whorl. Columella describing a narrow hollow spiral. 

 Altitude 6'3 mm., breadth 11"3 mm. 



The shell of another specimen was slightly larger and its spire 

 more raised, the measurements of this example being : altitude 

 8"5 mm., breadth 13'25 mm. 



Foot long and narrow, the hinder part somewhat com- 

 pressed laterally, the top being flattened beneath the shell, but 

 bluntly keeled for the last 3 mm., and ending in a short, 

 obtusely pointed projection overhanging the large caudal mucous 

 pore, the opening of which is diamond-shaped. Sole attaining a 

 length of about 8 mm. and a maximum breadth of about 3 mm. 

 in alcohol ; tapering near the hind end, but rounded at the 

 extremity ; tripartite by a pair of longitudinal grooves, the central 

 area being slightly narrower than the lateral areas, especially at 

 the hind end, where the grooves converge. Foot-fringe and lateral 

 areas of sole crossed by numerous transverse grooves. Peripodial 

 grooves well marked, curving upwards at the hind end in front of 

 the caudal mucous pore. A median longitudinal groove is present 

 beneath the shell, but does not extend to the hind end ; it gives 

 rise to oblique radial grooves sloping down towards the foot-fringe. 



Sides of foot sparsely mottled with dark patches and spots, 

 especially towards its hind end. Most of these dark patches occur 

 along the course of the peripodial grooves, and in a pair of ill- 

 defined dark bands that are present towards the hind end of 

 the foot, one on each side of the median dorsal zone, which is 



