120 The Molluscan Family Planorbidae 



Genus PLATYTAPHIUS Pilsbry, 1924 

 Type by original designation Planorbis heteropleurus Pils. and Van. 



1896. Planorbis heteropleurus Pilsbry and Y.an.4tt.\, Proc. Acad. Nat. Sci. Phil., 1896, 



p. 562, plate 26, figs. 1-3. 

 1924. Platytaphius Pilsbry, Proc. Acad. Nat. Sci. Phil., 76, p. 51. Type Pla7wrbis 



heteropleurus P. and V. As section of Planorbis. 

 1931. Platytaphius Thiele, Handbuch, Teil 2, p. 479. Type Planorbis heteropleurus 



Pils. and Van. As section of Planorbis. 

 1934. Platytaphius Pilsbry, Proc. Acad. Nat. Sci. Phil., 86, p. 59. Type Planorbis 



heteropleurus Pils. and Van. As section of Drcparwtrema. 



1934. Platytaphius Henderson and Rodeck, Jour. Pal., VIII, p. 268. Type Planorbis 



heteropleurus Pils. and Van. As genus. 



1935. Platytaphius Henderson, Non-Marine Moll. N. Amer., p. 254. Fossil. Cites two 



fossil species from Oregon. 



Shell (plate 79, figs. 10-12). Of medium size, ultradextral, moderately 

 solid, corneous-white, rather opaque, the surface with fine, close growth 

 lines; earlier whorls rather deeply and about equally sunken on the two 

 sides; convex, and strongly angulate or keeled in the middle, on the right 

 side; periphery conspicuously carinated on the left side, which is shallowly 

 vortex-shaped, the whorls nearly flat. Last whorl slightly wider on the right 

 than on the left side. Whorls three and one-half, all visible on both sides, 

 the last wider than the spire. Aperture very oblique, rounded-pentagonal, 

 the right margin produced forward (Pilsbry and Vanatta, 1896, p. 562). 

 There are fine punctations on the embryonic whorls. 



Animal. At present unknown anatomically. 



Geographical Distribution. Lake Titicaca, Peru. 



Geological Distribution. Pliocene to Recent fauna. 



Species Considered as Valid. Platytaphius heteropleurus (Pilsbry and 

 A'anatta I is the only recognized species. 



Remarks. In describing this peculiar mollusk, Pilsbry says: 'This 

 remarkable species is totally unlike P. titicacensis Clessin, P. montanus 

 d'Orbigny, and P. andecola d'Orbigny, species already known from this 

 Andean lake. It is most like P. andecola, but much flatter with differently 

 lilaced keels, and in fact, so diverse in characters that no profitable com- 

 parison can be made' (1896, p. 562). In 1924 (p. 51 ) , this species was made 

 the type of a section of Planorbis and in 1934 (p. 59), it was made a sec- 

 tion of the genus Drepanotrema. In a paper by Henderson and Rodeck 

 (1934, p. 268) , the authors state that 'it is so distinct that it might be better 

 to consider it a genus.' With this statement the present author is in com- 

 plete agreement for the general form of the shell is so distinct from that of 

 any other species of Drepanotrema that it does stand quite alone. W^hat its 

 real affinities are can not be known until its anatomy has been investigated. 

 It may belong near Drepanotrema or it may belong elsewhere. 



Henderson and Rodeck ( 1934, p. 268) have associated two extinct 

 molluscan species from the Pliocene of Oregon with Platytaphius. The 

 localities are sixteen miles southwest of Vale, Oregon. This locality is so 

 far removed from Lake Titicaca, in Peru (more than 5000 miles), that it 

 would seem impossible for species of any group without intermediate habi- 

 tats to become established so far apart. Yet the two species from Oregon 

 correspond fairly well with the diagnosis of the genus Platytaphius. Ad- 



