100 NEW SILURIC GASTROPODS 



forms included by Barrande under that genus, than they do any 

 other gastropods that have been described. In their lack of 

 ornamentation and their shallow sinus they seem to fulfill the 

 theoretic requirements for the hercynelloid ancestor. There is 

 some tangible proof that this is the close correspondence between 

 the adult shell form and outline of the species from the Bertie 

 and those of the young stages of the species from Bohemia. It 

 is evident that the forms in Bohemia were much more specialized 

 than those from the Waterlime, for even those from the lowest 

 European horizon, E 2, which corresponds to the Monroan in 

 America, already showed a pronounced radial sinus and strong 

 radiating striae. These two new species are so very different 

 from Barrande's type (H. bohemicaii) and so much more primi- 

 tive, that it would almost seem advisable to put them in a new 

 genus, except for the fact that the material from which they are 

 described is too poor to allow a complete and exact enough 

 description to be made for the founding of a new genus. In 

 case more and better material be discovered in the future, there 

 might then seem to be sufficient grounds for separating these 

 species from Hercynella, in which case I propose the generic 

 name Hercynellina. 



Habitat of Hercynella. 



The horizon in Bohemia in which the largest number of Hercy- 

 nellas has been found is F, or upper Monroan. Here they are 

 associated with vast numbers of graptolites and also with sponges, 

 trilobites and tentaculites. The fauna is undoubtedly marine, 

 and since it is well preserved and the Hercynellas also are 

 numerous and in good condition, there is no reason for question- 

 ing the marine habitat of the species in Bohemia. Furthermore, 

 the shells are comparatively thick, showing no lack of carbonate 

 of lime for impregnation. The one specimen from the Monroe 

 limestone of Michigan likewise has good marine associates, 

 though its macerated condition and the fact that no other 

 specimens have been found would leave it an open question 

 whether it was a true marine form or merely one swept out to sea 

 by land waters. The Hercynellas which have been found in the 

 Bertie waterlime seem to indicate conditions other than marine, 

 for their shells are exceedingly thin, as though available lime 

 were not abundant in the water in which they lived, and, 



