130 HOMORUS. 



Congo Free State, in the region of Lake Tanganyika (R. 

 P. Guilleme). 



Achatina marteli DAUTZ., Ann. Soc. Roy. Malac. Belgique, 

 xxxvi, 1901, p. 3, pi. 1, f. 1, and var. pallescens, f. 2. 



The photographic figures, copied on my plate, do not show 

 the color-markings of the shell. 



Genus HOMORUS Alters, 1850. 



Homorus ALB., Die Heliceen 1850, p. 196, sole species 

 Achatina cyanostoma. Edit. 2, p. 200, in part. not Homorus 

 Reichenb., Handbuch Spec. Orn. p. 172 (1853). KOBELT, 

 Conchyl. Cab. 1 Bd., lOte AbtheiL, p. 87, 1894. 



Shell imperforate, rather thin, turrited-conic, the spire usu- 

 ally a little contracted near the summit, which is obtuse and 

 rounded, the embryonic shell being subcylindric, the whorls 

 smooth at the suture (except in the subgenus Subulonci). 

 Post-embryonic whorls smoothish, typically covered with a 

 colored, brown-streaked cuticle. Aperture Achatinoid, the 

 columella concave, truncate below. 



Jaw rather strong, with numerous (21) flat ribs, and cov- 

 ered with strong vertical striae (pi. 62, figs. 15, 16, 

 H. cyanostoma, after Jickeli). Radula has 44.1.44 teeth; 

 centrals narrow, with a blunt, trilobate cusp without notice- 

 ably reflexed points. Lateral teeth large, with the mesocone 

 acute, ento- and ecto-cones well developed (pi. 62, fig. 17, 

 H. cyanostoma, after Jickeli). 



Type H. cyanostoma. Distribution, tropical Africa. 



Homorus differs from Achatina by the smallsize and sim- 

 ple coloration of the long-spired shell; but more fundament- 

 ally by its obtuse, rounded or bulbous apex, and shortly cyl- 

 indric embryonic shell. Pseudoglessula is closely related, and 

 has been ranked as a subgenus of Homorus by Kobelt; but it 

 has some special characters which it may be best to signalize 

 by generic rank. Homorus differs radically from Trichodina 

 in the form of the early whorls. 



There is at present no definite division between Homorus 

 and Subulina. A large series of African species have been 

 arbitrarily placed in one or the other genus; and the data 



