ORTMANN I TERTIARY INVERTEBRATES. 97 



Arenas. Large specimens from Arroyo Gio and Lake Pueyrredon pos- 

 sess at least part of the valves and are completely identical with those 

 from Punta Arenas. 



Record of specimens: Mouth of Santa Cruz River, 14 valves (young 

 and medium) ; Upper Rio Chalia, 8 casts (large) ; 30 miles north of upper 

 Rio Chalia, 4 casts; Arroyo Gio, 2 valves (large and small) ; Lake Pueyr- 

 redon, base of Tertiary, 2 sp. (large and small) ; Lake Pueyrredon, 600' 

 above base, 11 casts (small and medium); Punta Arenas, horizon V, 12 

 valves (medium and large). 



Distribution: Punta Arenas (Phil.); Patagonian beds of Santa Cruz (v. 

 Ih.), and Suprapatagonian beds of Jegua quemada and La Cueva (v. Ih.) ; 

 Perhaps in the Navidad beds (Lebu) of Chili (P. arattcanus Phil.). 



Affinities: V. Ihering considers this form a variety of P. pulvinatus 

 Lmck., and compares it with the form described by Hcernes as P. pilosus 

 L. from the Miocene of the Vienna basin. This is quite right, especially 

 as far as it relates to the sulci of the area. The larger Eocene species of 

 the genus (P. obovatus Lmck., pulvinatus Lmck., polymorphus Desh.) dif- 

 fer at a glance in the more crowded, and accordingly more numerous 

 sulci, while in the Miocene, Pliocene and Recent form, that has been 

 called by the Linnean name P. pilosus, the number of sulci, in individuals 

 of corresponding size, agrees closely with that of P. ibari. In P. pilosus, 

 however (see Hcernes,. 1870, p. 316, pi. 40, 41), these sulci are very in- 

 distinct, while in P. ibari they are well developed and sharp, and further, 

 P. piloszis differs from our species in the teeth of the hinge being more 

 distinctly geniculate, and in the radial striae of the surface being less dis- 

 tinct and more obscured toward the lower margin by the lines of growth. 

 Thus P. ibari has a distinctly Neogene appearance. 



Fain. PERNID^E Zitt. 



Gen. PERNA Brug. 

 32. PERNA QUADRISULCATA v. Ihering. 



PI. XXIV, Fig. 2"'". 

 1897 P- y* 1 - v - Ihering, in: Rev. Mus. Paul., v. 2, p. 231, pi. 9, f. 54. 



Shell thick, upper margin straight, anteriorly sharply angulated, pos- 

 teriorly alate, angularly produced and sinuate. Hinge broad, with four 

 distant, very broad grooves. 



