LOWER CARBONIFEROUS FOSSILS. 569 



Cliothyris crassicardinalis, var. nana. n. var. 

 PI. LXXI, fig. 9a. 



The form here referred to is a rare one, and I am in doubt whether 

 to consider it only young or dwarfed specimens of CI. crassicardinaUs, a 

 true variety of the same, or a distinct species. Its occurrence is restricted 

 to two or three localities, where it is not uncommon to find familiar types 

 represented by unusually small individuals. It has not been possible to 

 ascertain whether this shell is a true Athyris (sensu stricto) or belongs to 

 the genus Cliothyris, though the circularity of its outline favors the latter 

 reference. 



The shell is very small, nearly circular in shape, moderately convex. 

 Beaks small, surface ornamented by numerous close, regular, imbricating, 

 concentric lamellae. It occurs in a limestone and is always more or less 

 exfoliated. There is no fold or sinus, but both valves have a mesial flatten- 

 ing, which in some shells is quite marked. In size, shape, and general 

 appearance this form is very close to specimens of CI hirsuta from Spergen 

 Hill, Indiana. 



Length, about 0.30 inch ; width, nearly the same. 



Formation and locality : Madison limestone, east side of Gallatin River, 

 west of Electric Peak; Crowfoot Ridge, Gallatin Range, top of bed 25; 

 G. M. Wright. 



Cliothyris roissyi Walcott (non LeVeiHe"). 



Athyris royssii Walcott, 1884: Mon. U. S. Geol. Surv., Vol. VIII, p. 280, PI. XVIII, 

 figs. 9, 9a. 



I have referred to this species a single large Athyroid which, though 

 so exfoliated as to appear almost smooth, yet bears so strong a resemblance 

 to the specimen referred by Walcott to CI, roissyi (loc. cit.) that I can not 

 but believe them identical. There is, however, one striking difference, 

 namely, in the size of the ventral beak, that in my collection being of 

 medium size, the other extremely minute. But as both specimens are more 

 or less crushed, it seems that this is only an appearance due to relative dis- 

 placement of the two valves. 



The generic position of the form figured by Walcott, which shows very 

 clearly the overlapping spinose lamellae characteristic of Cliothyris, is 



