igzi.] Manipur Molluscs. 56 



/ 



From a geographical point of view the Indian species fall na- 

 turally into four groups, which may be defined as follows : — 



1. The Eurasian Group. — A small group of species found 

 in the higher valleys of the Indus system in the Western Himala- 

 yas and consisting of species identical or almost identical with 

 those of Europe. 



2. The Afghan Group.— Another small group, consisting of 

 species that bear considerable resemblance to the L. lagotis and 

 L. pcregra groups of the Palaearctic Region. The range of this 

 group extends from Afghanistan through the mountains west of 

 the Indus in Indian territory and thence across the Perso-Afghan 

 desert to Eastern Persia. 



3. The Indian Peninsular Group. — A group of three spe- 

 cies with numerous phases, varieties and mutations. It occupies the 

 whole of Peninsular India and the Indo-Gangetic Plain, and ranges 

 eastwards to Burma and northwards into the Lower Himalayas 

 east of the Indus. 



4. The Burmese Group.— We know comparatively little 

 about this group, which is probablv of Chinese origin in the main. 

 Its range probably extends from Upper Burma into Eastern As- 

 sam, but it occupies much territory in common with the Indian 

 Peninsular group. 



We are at present concerned with species in groups 3 and 4. 

 The Afghan forms have recently been discussed by us in another 

 volume ' of the Records and the Eurasian forms have still to be 

 compared in detail with their European representatives. Neither 

 of these groups is found in any part of Assam. 



We have stated our opinion that the Indian group consists of 

 only three species, thus agreeing with Nevill (loc. cit.) ; but a large 

 number of races, phases, varieties and aberrations have received 

 specific names. The three species are L. acuininata^ L,amarck, L. 

 ovalis, Gray and L. lateola, Lamarck. The last has been called L. 

 succinea, Deshayes, by some authors. We have to discuss here 

 only L. acuminata and L. ovalis. 



The Burmese group also comprises, so far as we are aware, 

 onl3' three species, viz. L. andcrsoniana, Nevill, L. slianensis, An- 

 uandale and L. mimetica, Annandale. The last is probably derived 

 from the Indian L. acuminata, but the other two are probably 

 of Chinese origin. We have here to discuss L. andcrsoniana and 

 describe a highly peculiar new species from Assam, probably related 

 to L. ovalis. The name we propose for it is L. ovalior. 



Before discussing individual species in detail it will be as well 

 to say something of the principles on which we have based their 

 classification. We had hoped to find some diagnostic features in 

 their anatomy and have examined the radulae and other internal 

 organs of most of the Indian forms with this object in view; but 

 we have been disappointed and are forced to the conclusion that 

 shell-characters, provided that a sufhciently large number of indi- 



i Aec. Ind. Mus. XVIII, pp. 39-52. pis. v-vii (iqii)). 



