NO. 1395. CAMBEIAy BRACHIOPODA—WALCOTT. 299 



.sharph' conical ventral valve. When the apex is broken off the cast 

 of a median apical callosity is seeiip/with the base of the cast of a 

 medium-sized foraminal tube. Th^ardinal scars are small and nearly 

 concealed by the cast of the strong- main vascular sinuses. There is 

 considerable range of variation in the size and lenglh of the median 

 ridg-e of the dorsal valve. One specimen shows a strong median ridge, 

 cardinal and central scars, and deeply excavated false deltidium. Sur- 

 face marked by tine concentric striie and lines of growth and very fine 

 undulating striae, that give the concentric stride a fretted appearance 

 when examined l)y a strong lens. 



The most nearly related species appears to be A. sahrinm of the 

 Shineton shales. Dr. Cr. F. Matthew has described a shell as Acrotreta 

 slpo that occurs with the ^Vsaphellus fauna, I am unable to detect any 

 specifi(; difi'erences l>etween it and A. hisecta from the same area. 



Formation and localifij. — ITpper Cambrian. Barrachois Glen, 4 

 miles south of Little Bras D'Or Lake, Cape Breton. Mr. Matthew's 

 types came from McLeod Brook, Cape Breton, Nova Scotia, and he 

 also identifies it from division C, 3c., at Navy Island, St. John Harbor, 

 New Brunswick. Mr. S. Ward Loper found many specimens at sev- 

 eral horizons in the shales on both sides of the Barrachois River near 

 the Boisdale road and for some distance north, also on the east branch 

 of the Barrachois River, (kpe Breton, Nova Scotia. On the west 

 bank it is associated with AmpJtellv.s honiphrayi var. as identified by 

 Dr. (t. F. Matthew. 



ACROTRETA? CANCELLATA, new species. 



The only specimen of this species in the collection has more the 

 form of Iphidea than Acrotreta. In its overhanging false area it sug- 

 gests Aet'othi/ra. Whatever the genus may be to which it belongs, 

 its cancellated surface serves to distinguish it from forms to which it 

 might otherwise be compared. This surface is formed by very fine, 

 raised, concentric lines or ridges of growth, crossed b}' sharp radiat- 

 ing lines which are seen only between the concentric lines. 



Formation and locality. — Ordovician Pogonip limestone, Round 

 Top Mountain, Eureka District, Nevada. 



ACROTRETA EGGEGRUNDENSIS Wiman. 



Acrotreta eggegrundeni^iii Wimax, Bull. Ueol. Institute, Upsala, No. 2, VI, 1903, 

 Pt. 1; Studien Nordljaltisohe Silurgebiet, p. 55, pi. ii, figs. 23-29. 



This species is of a characteristic Middle Cambrian type of Acro- 

 treta, represented in America by A. Idahoensh and A. hutorgal. The 

 surface is marked l)v unusually strong lines and ridges of growth and 

 the false area is well defined. It is quite distinct from other species 

 of the genus in European formations. 



