24 
PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. 
Length of the type, 17 mm.; height, 15 mm.; convexity of the two 
valves, 8 mm. 
Besides the well-preserved type, the species is represented by a cast of 
one valve and possibly by two other imperfect valves, that are referred 
with some doubt to the species. The hinge and other internal characters 
are unknown and the generic reference is, therefore, very uncertain. 
Locality and position . — From the Ammonite (Belgrano) beds ten miles 
east of Lake Pueyrrydon. 
Tapes (?) sp. 
Associated with the preceding species at the same place and horizon is 
another form of about the same size, but considerably more elongate, with 
the beaks nearer the anterior end, less convex and with smoother surface. 
The pallial sinus is deep, rather broad and horizontal. Represented by a 
nearly complete internal cast retaining small portions of the shell and by 
the imprint of a part of the surface of the same individual. 
Tellina sp. 
A single small internal cast retaining small portions of the shell is re- 
ferred to this genus on account of its form and general aspect. The 
valves are slightly twisted laterally ; anterior end broadly rounded ; pos- 
terior end obliquely subtruncate, much more narrow and somewhat 
shorter, than the front end ; ventral margin slightly convex ; beaks rather 
prominent ; surface apparently smooth. 
Length, 21 mm.; height, 13 mm.; convexity of the two valves, 5 mm. 
Locality and position . — Ammonite (Belgrano) beds ten miles east of 
Lake Pueyrrydon. 
SOLECURTUS (?) LIMATUS Sp. 110V. 
PI. IV, Fig. 10. 
Shell small, elongate oval, subequilateral, with very small, inconspicu- 
ous beaks ; dorsal and ventral margins very slightly convex ; anterior end 
regularly rounded ; posterior end slightly contracted, broadly rounded 
into the ventral margin below, more abruptly rounded or subangular 
above ; surface with a polished appearance but marked by numerous fine 
growth lines that vary somewhat in size. 
Internal casts show imprints of two very small teeth and subequal 
