. , lamellibranchiata. 549 



vanuxemia.] 



Fig. 9 of plate XL, represents what appears to be a large right valve of germana. 

 The specimen is preserved as a partial mould of the exterior. Another specimen 

 from the Galena near Wykofi may be said to be identical in its characters with the 

 original types of germana. The specimen represented by fig. 10 is one of a number 

 in which the balance of agreements is with the variety rather than with typical 

 grandis, while the original of fig. 11 was made by a small right, valve of which the 

 opposite seems to be true. 



Another variety was found in the Trenton of Tennessee by Prof. Jas. M. Safford, 

 and^sent to me for examination. The illustrations show that in its outline and 

 general appearance this new variety closely simulates variety germana and C. tenella. 

 It differs, however, in the tfeeth which are stronger and more curved than in those 

 forms, being on the whole more like those of C, gYandis and C. saffordi. As it marks 

 another stage in the developmlent of this type of shells it should receive a name. I 

 propose therefore that it be called Gyrtodonta grandis, var. intermedia. 



Mr. Sardeson has given the name luculenta {he. cit.) to a Hudson River form of 

 which the hinge and exterior of two fair examples are represented on Plate XL, by 

 figs. 13 and 14. This form I cannot now regard as specifically distinct from C. grandis, 

 since it is almost identical with var. germana, the only difference being small ones 

 in the hinge and that the umbones are somewhat larger in the luculenta. 



Two other stages in the development of this series of shells, in these cases per- 

 haps of specific importance, occur in the upper beds of the Cincinnati group at Rich- 

 mond, Indiana. These I hope to describe in another publication. 



■ Formation and locality.— The types of C. grandis and the var. germana, are from the upperTrenton 

 betwcQg Burgin and Danville, Kentucky. Casts of the species and variety have been found in the middle 

 and lower Galena near Cannon Falls, Kenyon, Ple&,sant Grove, Wykoff, Lime City, and other localities In 

 Minnesota; at Decorah, Iov?a, and Oshkosh, Wisconsin. The variety intermedia is so far knovyn only, 

 from the Trenton at Haynie's rnill. In Tennessee, where it occurs in association with Vanuxemia hayniana 

 Safford, sp. The rar. luculenta occurs in the shaly limestones of the Hudson River group at Granger and 

 other localities in Fillmore county, Minnesota. 



Mm. Beg. Nos. 8337, 8347, 4102, 8360, 8333. Var. luculenta 8332. 



Genus VANUXEMIA, Billings. 



Vanuxemia, Billings, 1858. Rep. of Progr. Geol. Sur. Can., p. 186. 



Shells ventricose, oblique, acuminate ovate to subcircular; ant-erior end very short 

 and small, the posterior broadly rounded. TJmbones full, prominent, beaks strongly 

 incurved. Surface with concentric growth lines only. Hinge strong, with teeth 

 as in Gyrtodonta, two to four, rarely more, cardinal, and two to four posterior lateral 

 teeth in each valve. Teeth frequently striated transversely, an elongated ligamental 

 area generally present. Two adductors, the anterior depression very sharply defined 

 and deep, and situated in a prolongation from the anterior end of the hinge plate; 



