18'J5.] MOLLTJSCA or THE ANDAMAS' AND NICOBAR ISLANDS. 439 



fatigable collector, and be added many new species to the list. 

 As Morcli states quite truly, Copenhagen was, one may say, at this 

 time the capital of the science of couchology, it being sufficient to 

 mention the names of Miiller, Chemnitz, Spengler, Fabricius, and 

 Regenfuss. 



With this previous work and material I am enabled to give a 

 very full list of what has been obtained there ; it does not profess 

 to be exhaustive, as I am aware that collections are constantly 

 arriving in this country, but I trust the list will be useful for 

 others to add to. For instance, I know of no Land-Shells having 

 been found on either of the small volcanic islands, and it would be 

 of great interest if any should occur, having reference to the 

 means whereby such forms can be transported. 



The difficulty of lauding on many of these rocky islets, and of 

 getting back to the ship, is so great that very few opportunities 

 occur, and then the time on shore is very limited, so that a good 

 deal has yet to be done. It is remarkable how very few species 

 range beyond the islands on which they have been found ; thus 

 there are only 8 species common to the Andumans and Nicobars, 

 while only 7 range on the south to Sumatra and Java, and only 

 5 north to Eurmah. However, there is a distinct and close 

 relationship in the past shown with Burmah and Arakan by so 

 many closely allied species, and equally marked is the paucity of 

 forms having an alliance with those of Peninsular India. Marked 

 diversity of form and restricted range is displayed among the 

 Operculates, in Cydu2'>horus especially, by the turbinate shells 

 of 0. leai, C. fuliaceus, &c., while Alyae us and Diplommatina are 

 very limited in species. No species of Clausilia has yet been 

 recorded from the Audamans, and only three from the Nicobars, 

 and they are very close allies. 



The genus Microc'/stina is represented by several species; although 

 M. cryptomphala from Lower Bengal was placed in it by me, yet, 

 as its anatomy is not known, this extension of the range is not 

 certain. Five species occur in Borneo, but the animal has yet to 

 be examined. 



The genus Plectopylis, so common in Burmah and N.E. India, 

 is absent. It is interesting to note the occurrence of Omphalo- 

 trojpis, a genus represented by numerous species in the Mauritius, 

 and here represented by 7 species ; but it does not occur in India 

 or on the mainland beyond the Andaman Sea. Hyalimax is 

 another genus with a similar range. The physical features of this 

 group of islands have been treated of by many authors, and their 

 position, as regards the whole volcanic line of action, is now defined 

 as one lying outside and to the west of it, and having its extension 

 to the south-eastward in the Nias Islands off Sumatra. 



Blanford and Medlicott, in the ' Manual of Geology of India,' 

 vol. ii. p. 732, may be consulted ; an interesting account by Mr. 

 A. O. Hume and the other members of an expedition to the islands 

 is given in ' Stray Feathers,' vol. ii. (1874). Still later Dr. Prain, 

 in the 'Proceedings of the Asiatic Society of Bengal,' April 1892, 



