810 CAMBRIAN BRACHIOPODA. 



Clarkella montanensis (Walcott). 

 Plate CIV, figures 2, 2a-<i. 

 Polytcechiaf montanensis Walcott, 1905, Proc. TJ. S. Nat. Mus., vol. 28, pp. 295-296. (Characterized and discussed 

 as below as a new species.) 



This shell was placed with Camerella calcifera until sections were made showing the 

 numerous septa supporting the spondylium and cruralium. In general form it is close to 

 SyntropMa rotundata Walcott, differing in the numerous supporting septa of the spondylium 

 which divide the umbonal cavity into five chambers. The material available for study does 

 not show the area in very good preservation; a delthyrium exists in the area of the ventral 

 valve, which is all that can be said. 



This species appeal's to be a direct descendant of the smooth, convex forms of SyntropMa, 

 like S. rotundata. 



FoKMATioN AND LOCALITY.— Lowei Oidovician : (302j) Limestone on the east side of West Gallatin (Gallatin) 

 River, above Gallatin, Gallatin County, Montana. 



