THP: PHILIPPINE MOLLHSKS OF THE GENUS PLANORBIS. 



By Paul Bahtsch. 



Axsidant Vnrator, Diriitiou of Molliiskn, U. S. Ndtioual Mvsevtii. 



Up to date onl}^ two spccie.s of PJanoTl>l)< have been known from 

 the Philippines. To these Maj. E. A. Mearns's explorations in Min- 

 danao have added two new forms, which are described and tigured in 

 the present paper. 



PLANORBIS (GYRAULUS) QUADRASI M Ollendorff. 



Phinorhis ( Gyranlui^) (juddnixi Molle.ndokff, Bericht. Seiick. Nat. ( Jes., HK).">, p. 115, 

 pi. Ill, figs. 11, lla-llc. 



The type locality for this species is Montalban. Luzon. The type 

 is said to have three whorls and measures: Greater diameter, 8.5 mm. ; 

 altitude, 1 mm. Von Mollendorff also reports it in the same publica- 

 tion from the island of Leyte. His tigure shows almost four instead 

 of three whorls as cited in the description. 



PLANORBIS (GYRAULUS) MINDANENSIS, new species. 



Shell lenticular, biconcave, thin, semitransparent, corneous. Upper 

 surface decidedly moi-e concave than the lower, showing all the whorls, 

 which increase evenly and rapidl}- in size. The entire upper surface 



Fig. 1.— Planokbis (Gyraui.us) jMinijanensis. 



is marked by numerous, quite pi'ominent, ii-regularly developed lines 

 of growth. Periphery of the last whorl marked by a slender keel. 

 The basal ])arts of the whorls are a little more convex than the upper 

 sides, with the incremental lines less strongly dcAcloped. The center 



Proceedings U. S. National Museum, Vol. XXXII— No. 1512. 



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