G12 Systematic Paleontology — Upper Dea-oniax 



limestone nodules of the Naples beds in Ontario County, ]N'e\v York, 

 show that the hinge may bear on its edge a row of minute denticulations 

 wliich is in accordance with the determination made by Xeumayr, but it 

 seems quite unlikely that these denticulations are homologous with true 

 liinge teeth, save in so far as they assist the articulation of the valves 

 and, it is certain that they are not always present. In the stronger ex- 

 pressions of this type of structure there is no difficulty in associating 

 germane members of this genus, but it is to be observed that the genus 

 passes by very easy gradation into that group which has been characterized 

 by the term Paracardium Barrande. We find the latter shells recogniz- 

 able by greater numerical development of the ribs, the lack of the charac- 

 teristic concentric ornament upon these ribs, and the general extinction 

 of the characteristics of Bucliiola; not that there is any fundamental dif- 

 ference in the structure of the two groups, but both are of the same 

 diaphanous, fragile character peculiar to the paleeoconchs, and in respect to 

 hinge structure both seem to be alike. There are species however upon 

 which each genus seems to have a distinctive claim. With the multi- 

 plication of the number of ribs the ornamentation of the surface becomes 

 progressively obscured, and while the latter may become quite extinct 

 there are forms in which the two features are combined and which, 

 hence, appertain as fairly to one of these divisions as the other. Para- 

 cardium doris Hall, which we find abundant in the New York and jMar}'- 

 land development of the Naples fauna is an excellent representation of 

 the fully developed Paracardium type. 



In New York the genus Buchiola reaches, as before observed, from the 

 early middle Devonican into the lower upper Devonian. It is in the latter, 

 the Naples fauna or the zone of Manticoceras intumescens, where the 

 genus attains its culminant development, and it is at this horizon also 

 that throughout the paleozoic faunas of the world the genus attains its 

 maximum. In Maryland the genus has not yet been recorded from hori- 

 zons other than those of the Naples fauna, while in the now thoroughly 

 well-known range of the genus in Germany it has very much the same 

 extent as in America, with its maximum in the lower upper Devonian, 

 species passing even higher into the stages of the upper Devonian. 



