9 8 
PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
Remarks: Our fragments from Santa Cruz do not show the external 
form of the shell. According to v. Ihering it is subquadrate, a little 
broader than high. The specimens Irom Lake Pueyrredon are chiefly 
casts ; one of them shows clearly the impressions of the lower margin of 
three of the cardinal grooves (see pi. XXIV., fig. 2*), agreeing with the 
specimens from Santa Cruz in being very broad and distant, which is the 
most prominent character of this species. Only part of the shell remains 
here. The casts indicate apparently a higher shell, but taking into con- 
sideration the great thickness of the shell at the anterior end, and the 
missing part at the posterior, which has been lost by fossilization, the 
outline of the Pueyrredon specimens would come near to that given by 
v. Ihering. I do not hesitate to refer them to v. Ihering’s species, since 
the characteristic feature of P. qiiadrisulcata is exhibited in one of them. 
Record of specimens: Mouth of Santa Cruz River, 9 fragments; Lake 
Pueyrredon, base of Tertiary, 2 sp. ; Lake Pueyrredon, 6oo' above base, 
4 sp. (2 of them young). 
Distribution : La Cueva, upper part of Patagonian formation (v. Ih.). 
Affinities: No known species of Perna can be compared with this one; 
but there is some resemblance to Crenatida amculifonnis Philippi (Navidad 
beds of Chili), but the latter is too incompletely known to permit any 
opinion in this respect. 
Fam. OS TREIDAE Larnck. 
Gen. OSTREA L. 
33. Ostrea torresi Philippi. 
PI. XIV, Fig. 3“X 
1887 O. torr. Philippi, Tert. Quart. Verst. Chiles, p. 215, pi. 48, f. 8. 
1899 O. torr. Ortmann, in: Amer. Journ. Sci., v. 8, p. 427. 
Shell in outline broader or narrower oval, rarely suborbicular ; mod- 
erately thick. Lower valve deeply excavated, upper valve flat. Area 
moderately large, triangular. Muscular impression about in the middle 
of the inner surface, only slightly lateral. Both valves with numerous, 
strong radial plaits, but on the upper valve these are less distinct and 
sometimes missing. 
Measurements: Length, 104, 117, 125, 131. An upper valve : 129 mm. 
Width, 74, 106, 74, 95. 102 mm. 
