857 



Rens. 



lected figs. 16, 17, dorsal and ventral views of a characteristic 

 specimen somewhat larger than common; 18, unusual, broad, 

 ventral valve; 19, dorsal cast, with muscular scars, dental cav- 

 ities, etc., 20, ventral cast with scars, and hinge plate impres- 

 sion. Characteristic radiating striae uf Rensselmria not ob- 

 served. If a different genus. Hall proposed the name Rens- 

 selandia. Found in an Upper Helderherg limestone at Water- 

 loo, Iowa. — In Pennsylvania, C. E. Hall, collected specimens 

 at Marshall falls, Monroe Co., in 1875, which he referred doubt- 

 fully to this species of J. Hall. VIII a. 



Rensselaeria marylandica. Hall. Pal. N. Y. l^ol. 3, 1859, 



^' 



s 



<?' 





/;' ^ 





/^ 



* ^ 







m 





\'/&k 



j^fj ^^p 



'^''^"^''^^hM 



(im^ ^ 



1 ,^ 



^raIl^.Y. 



page 461, plate 108,- selected figures 3 a^ b, c^ dorsal, ventral 

 and profile views ; ^, ventral interior, showing its teeth, dental 

 plates, and muscular scar ; k upper part of inside of dorsal 

 valve showing its broad hinge plates, bases of crura, raised 

 middle process, and hole (foramen) below the apex ; L diagram 

 (theoretical drawing) of the inside of a dorsal valve, showing 

 hinge plates, dental sockets, foramen, crural processes and 

 crural plate ; m^ diagram of long section of shell and internal 

 apparatus for connecting the two valves. Closely resembles 

 R. ovoides^ so abundant in the Oriskany sandstone of N. Y., 

 and may be only a variety; but no graduation from one form 

 into the other has been observed. Moreover R. ovoides, so 

 much larger and coarser, is found in the same rock with it, at 



