182 TRICHODINA. 



exhibit a more or less zigzag appearance. In other speci- 

 mens these broadish stripes are replaced by very numerous 

 and slender lines, which are more or less wavy and some- 

 times considerably interrupted and broken up." 



Genus TRICHODINA Ancey, 1888. 



Trichodina ANCEY, Bull. Soc. Malac. France v, p. 71, foot- 

 note 6, for "Trichodina marmorea Reeve (=barbigera 

 Morelet)" (1888). 



Shell imperforate, solid, turrited-conic, the summit conic, 

 not in the least mamillate; the apex minute, whorls rapidly 

 enlarging, flattened, often ribbed. Adult sculpture various. 

 Aperture small, Achatinoid, the columella truncate. Soft 

 anatomy unknown. 



Types T. marmorea (Rve.) and ~barbigera (Morel.). Dis- 

 tribution, Islands in the Gulf of Guinea; and the Comoro 

 Is., in the Indian Ocean. 



This group differs radically from Pseudoglessula, Homorus 

 and their allies in the structure of the early whorls, indicat- 

 ing a decided diversity in the young stages of the animals. 

 Homorus and Pseudoglessula have a pupoid or cylindric shell 

 in the late embryonic and early neanic stages, while 

 Trichodina and Bocageia have a trochoid shell. 



The species from the Comoro Islands are extremely similar 

 to those of the West African Islands, although separated by 

 the width of the entire continent. 



The species are arranged as follows : 



I. Columella distinctly truncate, Achatinoid (Trichodina). 

 a. Species of West African islands, sp. no. 1 to 6. 

 6. Species of East African islands, sp. no. 7 to 10. 

 II. Columellar truncation obsolete (Bocageia). 

 a. Prince's Island, species no. 11. 



Species of West African Islands. 

 1. T. MARMOREA (Eeeve). PL 55, figs. 96, 94, 95. 



Shell elongately turrited, narrow, somewhat cylindrical, 

 rather solid; whorls flatly convex, obliquely rather rudely 



