BRACHIOPODA. 389 



St ropli onu-na 



This variety in general appears to be closely related to Strophomena wisconsinensis 

 Whitfield,* but is readily distinguished in being less convex and in the very distinct 

 alternation of the striae. That species is clearly related to S. ruyosa Blainville, while 

 #. neglecta, var. acuta belongs to the S. incurvata group of strophomenas. Strophomena 

 vetusta James** is probably also closely related, but it is more evenly convex, never 

 has a flat central disc in the dorsal valve, while the outline is subquadrate. 



Formation and locality. Not rare in the upper portion of the Hudson River group at Spring Valley, 



Minnesota. 



Collectors. -E. O. Ulrich, W. H. Scofleld and the writers. 

 Mwt Reg. No. 5550- 



STROPHOMENA TBENTONENSIS, n. sp. 



PLATE XXX. FIG. 41. 



1847. Leptcena subtenta (partim.) HALL. Palaeontology of New York, vol. i, p. 115 



1883. Streptorhynchus gubtenta HALL. Second Annual Report, New York State Geologist, pi. xxxix, 



fig. 18. 

 1892. Strophomena subtenta HALL. Palaeontology of New York, vol. viii, pt. i, p. 251, pi. IX, flg. 18. 



This species is closely related to S. rugosa var. subtenta. The valves are, however, 

 thinner, the striae more delicate and the oblique wrinkling along the cardinal mar- 

 gins a more constant feature than in that species. The interior characters of S. 

 trentonensis are also less strongly developed than in S. rugosa. Whether from New 

 York, Minnesota, Kentucky or Tennessee, they exhibit the same undefined internal 

 markings when compared with the Hudson River group specimens of the latter 

 species. It is deemed also advisable to indicate this line of development towards 

 S. rugosa of the Hudson River group by separating the Trenton specimens on the 

 above characters with the name S. trentonensis. 



Prof. Hall (op. tit., 1847) found among the drawings of Mr. Conrad the figure of 

 a Strophomena with the name S. subtenta attached. The specimen from which this 

 drawing was made Prof. Hall says "is from a western locality" of the upper portion 

 of the Hudson River group of Ohio or Indiana. This form was again described and 

 figured by Meekf as S, plicata. As the essential difference between this form and 

 S. rugosa is only in the oblique wrinkling of the shell along the cardinal margins we 

 do not consider it of greater importance than varietal. 



Formation and locality. Not common in the Trenton shales at several localities to the south of 

 Cannon Falls, Minneapolis and Fountain, Minnesota. In the "Lower Blue beds' 1 at Janesville and 

 Beloit. Wisconsin. Near the top of the Trenton at Frankfort, Kentucky, and Nashville, T- 

 Trenton Falls, New York. A few examples apparently of thi= species have also been found in the Galena 

 shales in Goodhue county, Minnesota. 



Collectors. C. L. Herrick, W. H. Scofleld and the writers. 

 Mu*. Reg. No*. 6" -_ 183. 



*Gol. Wis.. vol. ir. p. 283. pi. ill, figs. 11-13; 1882. 

 "Cincinnati Quart. Jour. Scl. vol. i, p. 3*1; 1874. 

 + Pal. Ohio. vol. i, p. 81, pi. TL, figs. 4a-4h. 



