TROCHOMORPHA. O 



swollen between the lower end of the uterus and the opening of the 

 spermatheca duct, and at the upper end of this swollen portion there 

 is inside a whitish gland formed of one-celled club-shaped follicles (pi. 

 7, fig. 14a). This internal vaginal gland has not been noticed in 

 other species. Stoliczka lias published the anatomy of T. castra and 

 T. timoreusis (Journ. As. Soc. Beng. xlii), finding these species to 

 have the structure of typical Trochomorpha except for the very long 

 duct of the spernmtheca. 



The genus Trochomorpha inhabits a vast area, and is excessively 

 prolific in specific and varietal forms. Its range extends from India, 

 central China and the Liu Kin Is. on the north, southward to New 

 Guinea, the Louisiades and New Hebrides, and east to the Society 

 Islands. It is not known to occur in Australia, New Caledonia, or 

 any island having the Australo-Zealandic fauna, such as Norfolk 

 and Lord Howe. The species are in many cases founded upon 

 slight differences, and may become subject to some reduction as our 

 knowledge of their variation increases. For the present, it is 

 necessary to use great care in their description ; the width of 

 umbilicus compared with that of the base should always be stated. 

 The only genus with which species of Trochomorpha are likely to be 

 confused is the East Asian group Pledotropis ; this however differs 

 in the dilated columellar lip of the shell, etc. 



Subdivisions. 



Trochomorpha may be divided into three sections: (1) TROCHO- 

 MORPHA s. str. (of which Nigritella is a synonym), containing the 

 solid, opaque, trochiform species, mainly Polynesian, (2) VIDENA 

 Ads. for depressed, acutely keeled, thin shelled forms, with wide 

 umbilicus, and (3) SIVELLA Blanf. for species having the shell like 

 Videna, but with a very long duct to the spermatheca. 



The species of Videna occupy the entire area inhabited by the 

 genus, but are especially characteristic of the Philippines and east 

 Indies generally. Sivella is an Indo-Chinese group. 



Systematic position. 



The family relationships of Trochomorpha have been variously 

 estimated ; v. Martens (Albers, edit. 2) placing it under Nanina as 

 a subgenus, while Pfeiffer (Nomencl. Hel. Viv.) considers it a genus 

 between Leucochroa and Patula. Semper also places it among the 

 true Helices. The facts at present known incline me to view 



