RHYIS^CHOPORA 



515 



which has been investigated in these studies, and seems to be an addi- 

 tional character of generic value in Eliyncliopora. 



RHYNCHOPORA HAMBURGENSIS N. 8P. 



In the thin oolite limestone of the Kinderhook at Hamburg, Illinois/® 

 a small rh}Tichonelloid shell occurs in great profusion. The shell struc- 

 ture is distinctly punctate and a series of cross-sections, reproduced in 



o. o. O. <n. (TT) 



9 a> m O. Q, CD 



Figure 17. — Five Cross-sections of the rostral Portion of the Pedicle Valve and Sioe of 

 the Brachial Valve of Rhynchopora hamhurgensis n. sp. 



These two series of cross-sections (X 2%) are from specimens from the Kinderhook 



oolite of Hamburg, Illinois 



figure 17, shows that it has the same type of undivided hinge-plate as is 

 present in R. pustulosa. 



RHYNCHOPORA BEECHERI GREOER 



Cross-sections of this shell have not been made, but a series of very 

 excellent internal casts in chert exhibit not only its strongly punctate 

 shell structure, but also the presence of an undivided hinge-plate similar 

 to that in other members of the genus. 



Fl"i - : 



RHYNCHOPORA PERSINUATA (WINCH ELL) 



This species has not previously been referred to the genus Rhynchopora, 

 but study of an excellent example of an internal cast of the species from 

 the typical locality shows that the hinge-plate is undivided as in members 

 of the genus, but the specimen is not preserved in such a manner as to 

 exhibit either the presence or absence of the characteristic punctate shell 

 structure. On examining all available examples of the species, however, 

 one was observed in which the shell structure is distinctly punctate, so 

 that the two essential characteristics of the genus Rhynchopora are known 

 to be present. 



RHYNCHOPORA ? C00PEREN8I8 (SHUMARD) 



This species occurs somewhat commonly in the Chouteau limestone, 

 but a diligent examination of all the examples which have been available 

 for study has failed to demonstrate that the punctate structure of the 



i" Transactions of the Academy of Science of Saint Louis, vol. xvl, p. 465. 



