156 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Rhynchonella pugnus Davidson, 1861. Mon. Brit. Carb. Brach., p. 97, pi. xxii, figs. 1- 

 15. Ibid., Mon. Brit. Devonian Brach., 1865, p. 63, pi. xii, figs. 12-14; 

 pi. xiii, figs. 8-10. 



Missouriensis Meek, 1866. Geol. Survey Illinois, vol. ii, p. 153, pi. xiv, 

 figs. 4 a, b. Fig. 5 a of pi. C., 2d Ann. Eep. Geol. Surv. Missouri, 1855, 

 is also referable .to Rhynchonella pugnus, as stated by Mr. Meek. Not 

 R. Missouriensis Meek, 1868. Ibid, vol. iii, p. 450, pi. 14, fig. 7 a-d. 



alta Calvin, 1877. Paper read before the Iowa Academy of Sciences and 

 a named photographed plate distributed. 



pugnus Williams, 1883. Amer. Jour. Sci., vol. xxv, p. 99. 



The varietal differences among the Nevada specimens from the, same 

 layer or rock are quite marked, in this respect resembling the New York 

 forms described by Prof. H. S. Williams (Amer. Jour. Sci., vol. xxv, p. 97, 

 1883) and the English type illustrated by Mr. Davidson more than the Iowa 

 form of Mr. Calvin, although medium-sized specimens appear to be per- 

 fectly identical with the latter. 



The plications on the valves vary from eight to ten on some examples 

 and four to six on others. In the young and medium-sized shells the plica- 

 tions do not extend more than one-half the way up from the anterior margin, 

 while in the larger examples they reach nearly to the extremity of the beak. 



Under the name of Ehynchonella Missouriensis Shumard, Mr. Meek, loc. 

 cit., describes and illustrates a shell which he considered as closely allied to 

 varieties of Rhynchonella reniformis and E. pugnus, from the Carboniferous 

 limestone of England and Ireland. This type was what Dr. Shumard con- 

 sidered as the young of R. Missouriensis, describing and illustrating at the 

 same time a larger shell generically distinct from it, if we consider his fig- 

 ure, 5 a (2d Ann. Rep. Geol. Surv. Missouri, plate C), as a form of R. pugnus, 

 as suggested by Mr. Meek. Later, in vol. iii of the Illinois Survey, Mr. Meek 

 describes and illustrates the larger shell described by Dr. Shumard, and again 

 speaks of the relations between the smaller shell figured by Dr. Shumard 

 and R. pugnus, retaining the name R. Missouriensis for the former if the 

 latter proved to be identical with R. pugnus. 



In the collections of the American Museum of Natural History, Prof. 

 R. P. Whitfield showed me casts of Shumard's R. Missouriensis that prove 

 it to belong to the genus Camarophoria as determined by him. 



