(JO NEW YORK STATE MUSEUM 



Pterinea undata Hall (sp.) 



Plate 5, fig. 6 



Avicula undata Hall, Paleontology of New York. 1852. 2: 283, pi. 59, fig. 2 

 A single cast of the left valve. This, in its oblique form, short hinge 



line, prominent umbo, and much elevated, rounded umbonal ridge, agrees 



closely with this shell as described by Hall from the Rochester shale. The 



concentric undulations are also indicated on the cast. 



We are not aware that this species has been obtained in either the 



Canadian or western Guelph. The specimen described is from the upper 



Shelby dolomite. 



CONOCARDIUM Bronn. 183^ 



\j *j 



Conocardium sp. 



Plate 5, fig. 7 



Several small Conocardia, poorly preserved, have been noted in the 

 Guelph at Rochester. These indicate a shell somewhat similar to the little 

 known C. ornatum Winchell & Marcy 1 from the Niagaran dolomites of 

 Illinois, but seem to lack the sharp ornamentation of the umbonal ridge. 

 This ridge is greatly elevated, and the body of the shell is short, so that 

 both anterior and posterior slopes are steep, but the former is much the 

 more abrupt and is concave. The surface of the posterior slope bears nine 

 to 10 ribs with five to six on the anterior. 



Whiteaves mentions the frequent occurrence of a small Conocardium 

 in the Guelph at Durham and thinks it probably an undetermined species, 

 but gives no clue to its characters. 



MO mo tor sis Hall. 1847 



Cf. Modiolopsis subalata? Hall 



Modiolopsis subalatus? Hall, Paleontology of New York. 1852. 2: 285, pi. 59, 



fig- 7 



A somewhat incomplete cast of both valves, from the upper Guelph at 

 Oak Orchard creek, exhibits the characteristics of the Rochester shale 



'Boston Soc. Nat. Hist. Mem. i. 1866. p. in, pi. 2, fig. 15. 



