Rhyn. 



900 



Im.JS 10 



Rhynchonella sagerana, Winchell, Proc. Acad. Nat. Sci. 

 1862. Marshall group of Michigan. X. 



Rhynchonella sappho. See Stenoschisma sappho. Clay- 

 pole's specimen (unnamed) 12,335 (000, p. 151), is doubtfully 

 assigned to this species by G. B. Simpsoh (1889). Collected by 

 I. C. White near Bloomsburg, Columbia Co., Pa., from ^' Gats- 

 kilV strata in Rupert's Narrows. IX, 



Rhynchonella sordida. {Atrypa sordida^ Hall, Pal. N. 

 Y. Vol. 1, 1847, Trenton,) Emmons, Amer. Geol. I, ii^ 

 1855, 192, plate 10, fig. 16; small, circular, convex; 

 undivided ribs roughened by cross lines; no middle 

 fold. Supposed to be a young shell. Emmons. Tren- 

 ton formation. II c. 



Rhyn, stephani. See Stenoschisma stephani. VIII g, 



Rhynchonella striata, new species^ Simpson, Trans. Amer, 



Phil. Soc. Philada., 1889, page 444, fig. 

 10, based on specimens 9506, 9507^ 

 9508, of Randall's collections at War- 

 ren, wrongly labelled R. missouriensis. 

 Only the ventral valves of this species 

 have been observed, but they differ so 

 much from known forms that it is nec- 

 essary to consider them as belonging 

 to a new species. Shell subtriangular 

 ovate, apex pointed ; length and width 

 about eqi^al. Margins from the apex to below the middle nearly 

 straight, broadly rounded below, and at the base produced in 

 a broad extension. Ventral valve convex at the sides, de- 

 pressed at the middle. Mesial sinus beginning near the apex 

 and continuing to the base, becoming very broad as it ap- 

 proaches the front. Surface marked by thirteen plications, of 

 which five occupy the mesial sinus, the three central ones being 

 larger than the outer ones, but all smaller than those on the 

 other portions of the shell; plications subangular or angular. 

 There are also very fine radiating strias on the plications, three 

 in the space of 1 mm. The plications are crossed by fine 

 concentric striae, which are most prominent on the front of the 

 valve, becoming obsolete above, and also by stronger imbrica- 

 ting lines or varices of growth. The specimens observed have 



A. P.O. 



Tr. 1989 



