490 GEOLOGY OF OHIO. 



PULMONIFERA. 



The existence of shells of terrestrial air-breathing Mollusca in the 

 Coal Measures of this country was first made known in the year 1851, 

 when Sir Charles Dyell and Prof. J. W. Dawson made known their dis- 

 covery of Pupa vetusta in the coal-beds of the South Joggins, Nova 

 Scotia. Since that time there have been several additional species dis- 

 covered in the same region, and others in the Coal Measures of Indiana. 

 In the Am. Jour. Sci. for November, 1880, Prof. Dawson has given a 

 summary of the species known from the coal formations up to that time, 

 and also described what he supposes to be a similar form from the Devo- 

 nian plant-beds of St. John, New Brunswick. At the time Prof. Dawson's 

 memoir appeared I was working on the form herein described, from the 

 Upper Coal Measures at Marietta, Ohio, which has proved to be so 

 entirely distinct from any of those previously known that it became nec- 

 essary to found a new genus {Ajithracopupd) for its reception, which was 

 published in the above-mentioned journal, February, 1881. 



All the species known up to the time of Prof. Dawson's paper were 

 supposed to belong to the inoperculate division of the terrestrial Gaster- 

 opods, and had been referred to the Heucid.E and Pupine^. In making 

 the studies of the Onio shell I had obtained, through the kindness of 

 John Collett, Esq., State Geologist of Indiana, specimens of the two forms 

 from that State, and in freeing them from the matrix I discovered that 

 the species Dawsonella Meeki Brad, possessed not only the reflected and 

 slightly thickened lip described by its author, but that the inner lip and 

 much of the umbilical region were covered by a thickened and flattened 

 callus closely resembling that of Helicina, furnishing strong presumptive 

 evidence that it had been provided with an operculum, like the shells of that 

 genus. If this view of its nature is correct, it would place it with the 

 Helicinid.E in the operculate section of the Pulmonifera. The Ohio shell 

 has also some peculiar features that are not recognized among any of the 

 Pupa-form species heretofore described from this formation. It is of 

 small size, and the general form is similar to that of the group of the 

 Pupae usually referred to the genus Vertigo ; minute shells with a nearly 

 vertical aperture, armed with several projecting tooth-like points within 

 its cavity. This shell not only presents these same features, but the ad- 

 ditional one of having a small, nearly circular notch in the peristome 

 near the upper end of the outer lip, very closely resembling the minute 

 pore-like notch occurring near the upper angle of the aperture in the 

 genus Pupina Vignard; or that seen in Anaulus Pfieffer. This latter 

 feature is not present so far as I am aware in any genus of operculated pul- 

 moniferous shells; at least not in the same degree nor with the same ap- 

 parent purpose that it occurs in the operculated genera above mentioned. 

 The last volution is also flattened or contracted on the back in a very 

 similar manner to that of Pupina, as well as of man}'- of the Pupae. It 

 would therefore almost seem as if in this little shell, of this earl} r age, 



