78 zo^iTiD.i:. 



sides of the head forming a distinct tract. Lobes of the mantle 

 well developed, the rujlit and left shell-lohes hoth present, short or 

 elongate and generally pointed, extending in some species nearly or 

 quite to the apex of the shell, and constantly in motion. 



[The left shell-lobe has been found absent in M. atricolor from 

 the Muni pur Hills. 



In the genitalia, commencing at the generative apertm'e, the 

 penis-sheath is a moderately long cylindrical tube (larger near the 

 aperture) as far as the sharp bend at tlie epiphallic portion ; the 

 tube continues thence to the retractor-muscle attachment, and 

 so far it may be compared with the male organ of Ariophanta. 

 It is continuous still f lU'ther, forming a closely-coiled ccecum, tlie 

 coil more or less conspicuous or becoming an indistinct muscidar 

 mass. In three species from Sikkim the csecum is long, free, and 

 uncoiled, probably an early stage in its development. • The 

 retractor nuiscfe attachment, in this case, is at the basal end of the 

 Ccccum ; the epiphallus is short. The kale-sac is close to the junction 

 with it of the vas deferens, and is either a long fiagellum, a short 

 divei'ticulum, or a blunt knob. The dart-sac or amatorial organ 

 is usually large, long, and cylindrical, the dart muscular. The 

 spermatiieca is elongate, more or less club-shaped, sometimes v. ith 

 a bulbous termination ; its shape is necessarily dependent on 

 whether it is empty or containing one or more spermatophoi-es.] 



The coiled csecum is replaced in if. pedina &c. by a simple 

 diverticuliun, to the end of which the retractor muscle is attached 

 as iu Ariophanta. [This is a doubtful species of the genus.] 



Odontophore : teeth of similar type to those oi Ariophanta : the 

 rhacbidian (central) teeth tricuspid ; the admedians broad, 10-30 

 in number, about 100 to 160 in the row, bicuspid or partly (the 

 inner teeth) tricuspid, the inner cusp disappearing on the outer 

 teeth ; outer laterals narrow and usually with two cusps through- 

 out, either both terminal or one on the outside occasionally lower 

 down, rin some species the end of each lateral tooth is merely 

 notched ; in a few it is aculeate.] 



There has been considerable discussion as to the generic term 

 Macrocldamys. It was first published by Benson in 1832. and 

 also a specific name 31. indica, but no description was given, and 

 in 1834 it was replaced by Tanycldamys, also undescribed, said to 

 be the same as Gray's Nanina. In 1847 Gray adopted Macro- 

 cJdami/s, Benson, as a subgenus of Stenopus, Ariophanta and 

 Nanina being other subgenera, and he named Heli.v vitrinoides as 

 the type species of Macrochlamys. The shell probably, and the 

 mollusc certainly, called Heli.v vitrinoides by Gray was an Indian 

 species, and, as nearly as can be determined, 31. petrosa or 31. per- 

 plana. According to the rules of nomenclature generally adopted, 

 the term must he accepted as dating from Gray's quotation of it 

 in 1847. The Orohia of Albers is identical, being also founded on 

 the supposed H. vitrinoides from India [which at that time included 

 many different species in Bengal and even pedina of Bombay]. 



