president's address. 249 



merely to extract one single character, the odontophore, whicli, 

 valuable in one respect, is useless, except -when taken in conjunction 

 with all the other characters. 



The genus Macrochlamys, originally named by Benson from the 

 presence of the peculiar mantle lobes which play over the surface of 

 the shell, being a well-known genus, and the richest in species 

 of the whole family, with an extensive range, I shall take it first, 

 show the modifications the animal presents, and then pass on to other, 

 more or less similar genera. The typical Macrochlamys (section A) 

 is a common form in Calcutta, extending thence up the Gangetic 

 Valley, from the Rajmahal Hills to Allahabad, in the north-west 

 Himalaya as far east as Murree, where M. splendens is recorded by 

 Theobald. M. Flemingi is also found there. A yet undescribed 

 species, allied to this last, I have received from the Kuram Valley. 

 The genus occurs eastward from Darjiling, the Bhutan, Dafla, and 

 Singpho Hills,^ by the Naga Hills, the plain districts to the south, 

 and away to Arakan and Pegu. 



In addition to the presence of shell-lobes on both sides of the body 

 and division of the left neck lobe into two distinct portions, the most 

 noticeable character of the typical form (section A) is to be found in the 

 genitalia. This consists of a coiled, coecum-like appendage, where the 

 retractor muscle is given oif from the male organ. Still, the characters 

 of the typical Calcutta species, M. Hardwickii, are not constant over 

 the area I have indicated. 



In the Munipur and Naga Hills and North Burma a form is met 

 with, M. atricolor (section B), which ranges to Bamao in North 

 Burma. In this the left shell lobe cannot be seen, while, on the 

 other hand, the right shell lobe is enormously developed, and in life 

 must extend right across the shell : the long flagellum of the 

 male organ is reduced to a mere rounded knob. Another departure 

 from the type is M. Cacharica (section C). In this the amatorial 

 organ is absent. This variation is not an accidental matter, as 

 some malacologists might suppose, but seems constant in all the 

 specimens I examined, and a similar modification is to be found in 

 other genera of the Zonitidse, while Pilsbry has noted the loss of this 

 organ in other families with which he has dealt. 



Let us turn next to notice two genera, peculiarly distinct in their 

 shell characters from Macrochlamys, with its thin, glassy test. These 

 are Oxytes and Bensonia, with large, solid, often shai-ply keeled shells. 

 Again, we meet in both with the coiled coecum from which the retractor 

 muscle springs, and which in Orohia is enormously developed. This 

 character, I may j)oint out, I have never seen in any other Indian 

 genus besides these. "Whence it is derived, and what its special 

 function may be, I am at a loss to say. Oxytes and Bensonia possess 

 no shell-lobes to the mantle, but have the left dorsal lobe divided into 



^ The species from these hills remains to be named and described. It is small, of the 

 type of M. levicula, and although only 12 mm. in diameter, every character, 

 even to the coiled coecum, is present. Size, therefore, has little to do with the 

 simplification of the genitalia. 



