FOSSILS OF THE CAMBRIAN. 



In the Eureka District it is associated with the same species at the same 

 relative geological horizon. I now have before me Mr. Meek's type, and 

 also the type of Kutorgina minutissima H. & W., from the Eureka District. 

 They evidently belong to one species and do not vary from each other more 

 than individuals from the same locality. 



The generic reference of the species by Messrs. Hall and Whitfield is 

 followed, as from all comparable characters the species is closely allied to 

 the type of the genus Kutorgina cingulata Billings. 



As yet no evidence has been obtained of the presence of a pseudo-del- 

 tidium similar to that in Iphidea lella Billings. Mr. Meek failed to detect it 

 in working away the matrix from the specimens he used, and the same is 

 the case with the material from the Eureka District. From the fact that 

 the pseudo-deltidium is often absent in specimens of a well-marked species 

 allied to /. bella now before me, and the great similarity of the false 

 area of the larger valves of it and K. seulptilis, when in that condition, I 

 strongly suspect that if we had more perfect specimens the concentric sur- 

 face lines would not stop at the margin of the triangular space, but cross a 

 pseudo-deltidium, as in I. bella. 



As stated by Mr. Billings, the genera Kutorgina and Iphidea are closely 

 related to each other, and while it is convenient to have the two genera to 

 refer such forms as K. sculptilis and /. betta, with our present knowledge of 

 the two genera, Iphidea cannot be considered as a well-established genus, 

 although it is quite probable that if we had the interior of the shell of each 

 form it would be necessary to distinguish them as Mr. Billings has done. 



Formation and localities. Upper Cambrian. Secret Canon shale on the 

 east side of Secret Canon; shaly limestone in passage-beds between the 

 Cambrian and Silurian on the first ridge east of the Hamburg Mine, Eureka 

 District, Nevada. Also, on the east side of the Gallatin River above Gal- 

 latin City, Montana, as labelled in the collections of the United States Na- 

 tional Museum. 



