Rhyn. 



892 



4-2 



Rhynchonella maera. Whitfield, Bull. 3, Am. Mus. 1882, 



plate 6, figs. 40, 41, 42. {Camaro- 

 toria ? wortheni^ which see above. 

 Also Rhynchonella woriheni^ Hall. 

 Trans. Alb. Acad. Vol. 4,1856.) Ool- 

 ^9. lett's Indiana Report of 1882, plate 

 29, fig. 40, 41, 42. Spergen Hill. Suhcarh, limestone. XL 



RhynchLonella medea, Billings. Geology of Canada, 1863, 



Or 7\ ilHilii ^^^ P^^® ^^^' ^^* ^^^ ^' dorsal valve. 



In the Corniferous limestone for- 

 mation of Upper Canada. Villa. 



Ylll-X 



APS 



Tr 1883, 



Rhynchonella medialis, Simpson. Trans. Amer. Fhil. 



Soc. Philada., 1889, page 444, fig. 9, based 

 on Sp. 9509 ; shell broaply oval or sub- 

 trigonal in outline ; height a little less than 

 the width; greatest width about two- 

 thirds the length of the shell from the 

 beak. Margins from the apex to the 

 widest portion of the shell nearly straight, 

 then abruptly rounding and slightly produced in front in a 

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

 pressed in the middle; mesial sinus commencing at the apex 

 and growing wider to the base, where it occupies fully one- 

 half of the width of the valve. Dorsal valve unknown. 

 Surface marked by about twenty plications, of which eleven 

 occupy the mesial sinus and are smaller than those on the 

 other portions of the valve, there being five in the same space 

 occupied by three of the others; plications rounded or suban- 

 gular. There are also very fine radiating striae covering the pli- 

 cations, four or rive in the space of 1 mm. The plications are 

 crossed by lines or varices of growth. No concentric striae have 

 been observed, though they may occur on more perfectly pre- 

 served specimens. The specimen from which the above de- 

 scription was taken has a height of 25 mm., and a width of 

 30 mm. This species is associated with Ehynchonella^ but may 

 be readily distinguished by its size and the much larger num- 



