280 BULLETIN OF THE 



Streptorhynchus sp. 

 A single fragment of a dorsal valve represents this genus. Part of the 

 . cardinal process is exposed, showing that it belongs to the group character- 

 ized by a high ventral area and a long cardinal process, for which S. Halli- 

 anus Derby may be taken as the type. It is marked by a distinct median 

 depression, which, if constant, will distinguish it from any species known to 

 me. 



Chonetes glabra Geinitz. 



Chonetes glabra Geinitz Carb. und Dyas in Nebraska, p. 60, PI. IV. Fi^. 

 15-18. 



This characteristic species of the North American and Brazilian Coal 

 Measures is represented by several specimens on a slab from Yampopata. 

 Toula has also identified it from Cochabamba. 



Productus costatus? Sowerby. 



This form appears to be the most abundant fossil at Yampopata. It is 

 identical with the common form of the North American Coal Measures, as a 

 careful comparison of numerous well-preserved specimens proves. I follow 

 Hall and Meek in questioning its identity with the European P. costatus. 



Judging from d'Orbigny's and De Koninck's figures, P. Inca d'Orb. is 

 identical with this, differing only in being a little larger than any of Mr. 

 Agassiz's specimens. European palaeontologists have referred P. Inca 

 to P. semireticulatus Martin, but it is certainly much more like P. costa- 

 tus ? than the North American and Brazilian forms referred to Martin's 

 species. These last, when well preserved, are covered with very numerous, 

 closely set hair-like spines quite unlike the few scattered coarse spines char- 

 acteristic of P. costatus. P. Inca appears to have had a spiny covering of the 

 latter kind, as had also many of the European forms of P. semireticulatus 

 figured by Davidson and De Koninck. As specimens usually occur with the 

 spines denuded and the scars more or less obscured by weathering, the two 

 forms of the so-called P. semireticulatus are almost indistinguishable, though 

 appearing very different when perfect. To unite them, as is usually done, is 

 to ignore one of the best specific characters among shells of this class. 



The collection contains a few casts in red sandstone from the island of 

 Titicaca, that appear identical with the Brazilian forms of P. semireticulatus. 



Productus Chandlessii Derby. 



Productus Chandlessii Derby, Bull. Cornell Univ., Vol. I. No. 2, p. 51 , PI. IV. 

 Compare P. uolivicnsis d'Orb. 



A single specimen from Yampopata is identical with the Brazilian form to 



