108 OBBA. 



cavity of the penis is strongly, irregularly plicate or papillose. It 

 is encircled by a feather-like glandular appendix (pi. 39. fig. 12), 

 the follicles of each side of which unite into two separate ducts 

 sunken into the cavity of the penis (pi. 39, fig. 13, section of the 

 gland). See pi. 39, fig. 11-13, 0. planulata. 



Distribution, Philippine Islands, with a few forms in northern 

 Celebes, Halmaheira, and Ceram. 



This group, like Cochlostyla, seems to have originated in the Phil- 

 ippine Island area. A few stragglers are found to the southward, 

 as is also the case with Camoena and some other typically Philippine 

 groups. 



Obba differs from Camcena chiefly in the less capacious shell, with 

 subhorizontal aperture and continuous peristome ; in the possession 

 of a glandular appendix on the penis, the short spermatheca duct, 

 and the smooth jaw. It differs from Planispira in the raised parie- 

 tal callus and the keel of the shell, which is characteristic of all the 

 species when young, and most of them when adult. The teeth are 

 like those of Camcenella and Planispira. The anatomy of 0. plan- 

 ulata, listeri and basidentata has been examined by Semper (Reisen, 

 Landmoll., ii, p. 120) ; the jaw of rota by Morch. 



In Vol. VI of this work the writer stated that Helix mamilla was 

 the type of Obba, following v. Martens. But in 1847 Gray selected 

 H. planulata for the type. The genus must, therefore, be restricted 

 to species allied to planulata. 



(Group of O. planulata.') 



O. papilla Mull., vi, 216. O. planulata Lam., vi, 220. 



v. heroica Pfr., vi, 217. aurieulata Swains. 



O. listeri Gray, vi, 218. papilionacea Val. 



v. costata Semp., vi, 219. eollapsus Perry. 



O. gallinula Pfr., vi, 219. v. sarcochroa Pils., vi, t. 68, f. 



v. morongensis Mlldff. viii, p. [85. 



[270. O. calcar v. Mart., vi, 221. 



( Group of 0. moricandi.) 



O. moricandi Sowb., vi, 222. O. scrobiculata Pfr., vi, 224. 

 O. basidentata Pfr., vi, 223. O. rota Sowb., vi, 225. 



O. livesayi Pfr., vi, 223. O. platyzona Mlldff. 



