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. nOV. 

 PL 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 



