1S60.] Contributions to Indian Malacology. 127 



Hab. in sylvis, prsesertim prope arborum radices, ad apices montium 

 "Nilgiri." Yar. est, peristomate quinque dentato, dente nno minimo 

 versus sinum aperturse, tribus normalibus, uno minuto juxta umbilicum ; 

 denfce ad marginem coluniellarem alteris latiore, quae prope "Avalan- 

 cbe," ad pedem montium " Koondab" habitat. 



This species appears to be more abundant than the previously 

 described form, Str. Perrotteti* Petit, from which it differs in its 

 much smaller size, and despite this, in the greater development of 

 its teeth, and also in the presence of two lamellae instead of one 

 on the callus joining the margins of the peristome. It appears to 

 inhabit only the more southerly portions of the hills, but our 

 researches have not been sufficiently extensive to render this a 

 certainty. Str. Perrotteti occurred at Neddiwuttom, and on the 

 hills N. of Ootacamund ; Str. Watsoni we found S. of Ootacamund, 

 and the variety at the base of the Koondahs. Both were obtained 

 at an elevation of 6000 to 7000 feet. Although the variety differs 

 slightly in the teeth, in the presence, viz. of two teeth which are 

 absent in the normal form, these additional projections are so very 

 minute that they might easily become obsolete, and probably addi- 

 tional specimens might shew a complete gradition, while the shells 

 are so exactly similar in every other detail of form, that we have no 

 hesitation in pronouncing them identical. 



Explanation of figures. 



1. — Opisthostoma ISTilgiricum. Natural size. 



2, 3, 4. — The same magnified 90 diameters (900 times). 



5. — Scalariform costulation further enlarged. 



* Or is this Petit's original species and that described by Pfeiffer distinct f 

 In that case the names may be exchanged. 



s 2 



