1891.] LAND-SHELLS FROM BORNEO. 23 



obtained by Colonel Beddome in Travancore. Sitala is another 

 genus having a similar distribution, and one section of it (represented 

 by the peculiar little shells S. tricarinata and S. subhilirata of the 

 Nilghiri and Andaman Islands respectively) finds a representative 

 species in Borneo in Sitala kusana. When the intervening countries 

 and islands come to be better known, other allied forms will no 

 doubt be found. 



The closer the external characters of the animal are looked at, 

 and the more an attempt is made to combine these with the form of 

 the shell for the purpose of generic classification, the greater are the 

 difficulties met with. Dr. von Martens found this so much the 

 case when he took up the Land-shells of Eastern Asia, that he fell 

 back on to the shell alone. If, however, we go further and take 

 the internal anatomy, especially the points of difference in the re- 

 productive and other organs, and the odontophore, which has been 

 so well done by Professor Semper in the same region, we do find 

 some well-marked differences, and these we discover have but little 

 bearing on the form of the shell, which may be considered as of 

 secondary importance. It is to be expected that modification of 

 the internal structure of the animal is brought about much more 

 slowly than change in the shelly covering, and that it is conse- 

 quently far more persistent. The first is a combination of many 

 different organs, a change in one affecting all the others, while the 

 shell is a single structure merely secreted by the mantle, and affected 

 rapidly by change of climatic conditions and the nature of the rock 

 on which the animal lives. 



When such a sounder system of classification has been thoroughly 

 worked out, we shall be able to trace with some degree of exactness 

 the areas over which certain genera of Land-Mollusca extend. Then 

 noting how such areas have been affected by the more recent geolo- 

 gical changes leading up to the present outlines of the land and the 

 intervening seas, we may be enabled to contemplate and draw some 

 conclusions as to how far present distribution has been dependent 

 on and connected with such changes. 



In the descriptions of the species which follow, I have attempted 

 to show how very different are details of the anatomy of the Bornean 

 Helices when compared with those of very similar-looking shells of 

 the Indian region. 



Fam. ZONITIDiE. 



Vaginula kasselti, v. Martens, Preuss. Exped. Ost-Asien, Land- 

 schneck. p. 176, t. v. figs. 2, 4 (1867); Fisch. Nouv. Arch, du 

 Mus. vii. p. 158 (1871). 



Hub. Borneo, near Benkajang. 



Vaginula bleekeri, Keferst. Zeitschr. f. wiss. Zool. 1865, p. 118, 

 t. ix. figs. 1, 2 ; V. Martens, Preuss. Exped. Ost-Asien, Land- 

 schneck. p. 177 (1867) ; Fisch. Nouv. Arch, du Mus. vii. p. 161 

 (1871). 



Hub. Sarawak {Boria and Beecari). 



