MOLLUSCA OF INDIA. 



91 



colour. Spire subconical, but little raised, apex obtuse ; suture 

 smooth, scarcely impressed, sometimes margiuate. Whorls 5, very 

 slightly convex, regularly increasing in size, the last not descending, 

 rounded at the periphery, convex below. Aperture obli(iue, lunate, 

 broader than high. Peristome thin, simple, slightly curved when 

 viewed from the side ; margins distant and united by a thin callus ; 

 the columellar border vertical for a very short distance, slightly 

 reflexed. 



" Major diameter 0-44, minor 0-38, axis 0*22 inch. 

 "This shell belongs to the group of thin, more or less depressed 

 forms allied to the type usually known as 31. vitrinoides (M. in- 

 diciis), Benson. It appears, so far as I can see, to be undescribed, 

 as is also, I believe, an allied form of darker colour, and with a 

 sabangulate periphery, occurring at Trichinopoly and elsewhere in 

 the neighbourhood of the Coromandel coast south of Madras. The 

 animal of M. platycldamys is chiefly distinguished by the peculiarly 

 broad shell-lobes, which, instead of being narrow aud attenuate 

 towards the ends, as in most species, are broad and flat, so as some- 

 times to cover the whole spire, and usually to conceal all except a 

 narrow band. These lobes somewhat resemble those of Helicanon. 

 The lobe above the caudal gland is very much smaller than it 

 usually is in Ilacroc/damys, and rounded, not horn-shaped. 



" This shell is common in the island of Bombay aud neighbouring 

 lowlands on the west coast of India, and I have seen a form 

 from the hills of the Wynaad in Southern India that appears un- 

 distinguishable. I have also several specimens of a Macrocldamys 

 from the ancient town of Champanir, near Broach, that may very 

 possibly be a variety of M. platychlamys. The specimens are larger 

 than the Bombay types, an adult measuring 16 mm. by 14 mm. in 

 its two diameters, and some individuals attain even greater dimen- 

 sions ; the mouth, too, is rather more convex beneath, but other- 

 wise the two forms agree very closely. The figure (in Journ. Asiat, 

 Soc. Bengal) gives the idea of a rather thick shell, and the form of 

 the mouth is incorrect, being too convex below, and consequently 

 too high in comparison with the breadth." 



The surface of the shell above, highly magnified, shows no longi- 

 tudinal striation, only the irregular transverse streaks of growth, on 

 the under surface; distant, parallel, fine striation, at irregular 

 distances, is very well seen. 



Animal (PI. LXXXIV. figs. 1, 1 rt). Very dark grey, the lobe 

 over the mucous gland rather large ; the usual peripodial line and 

 fringe. Sole of foot with a strongly marked central area. A very 

 long right shell-lobe, wide near the respiratory orifice, and nar- 

 rowing posteriorly. The left shell-lobe very broad and quadrate 

 in outline and lengthened. Both these lobes are very black and 

 papillate. 



The buccal mass is compact and globose ; the salivary glands are 

 in two distinct masses. 



The odontoplwre. The central tooth has broad strong cusps on 

 both sides, about halfway down the basal plate. The median teeth 



