ANNOTATED CATALOGUE. 453 



strate that a widely differentiated land molluscan fauna existed during 

 the Coal Measure period, if not much earlier. . 



If the species which Dr. Dawson described under the name of Zonites 

 prisons , * from the Coal Measure strata of South Joggins, ISTova Scotia, 

 is really a Zonites, or a closely related form, we have proof of the remark- 

 able fact that the family Arionidae was well established in the Carbon- 

 iferous age. The correctness of the reference of this species to the 

 Arionida3 being accepted, we naturally conclude that other members of 

 the family have existed somewhere during all the time that has 'elapsed 

 since the Carboniferous age; but yet remains of no other representa- 

 tives of the Arionida3 are now known to exist in any North American 

 strata., if we except the one mentioned below. Copies of Dr. Dawson's 

 original figures of Zonites prisons are given on Plate 2. His specimens 

 were found associated with Pupa vetmta and P. bigsbyi Dawson, both 

 of which species are mentioned in their order on following pages. 



Mr. T. A. Conrad published a form under the name of Helix (Zonites) 

 marginicolaj from Bridge Creek, Oregon, which probably comes from a 

 fresh-water Eocene deposit. His specimens seem to have been very im- 

 perfect and unsatisfactory. A copy of his figure is given on Plate 32. 



HELICIDJE. 



Among other molluscan remains that have been discovered in the 

 Coalmeasure strata of Indiana and referred to the Pulinonata is a form to 

 which Professor Bradley gave the generic name of Dawsonella? describ- 

 ing the species under the name of D. meekii.\ Dr. Dawson, in comment- 

 ing upon this form, expresses the opinion that it belongs to the Helicidae 

 "near Helix (Triodopsis) palliata and H. (Stenotrema) monodon;" but 

 Professor Whitfield expresses the opinion that it was an operculate shell 

 resembling Helicina.\\ 



For present convenience, and without reference to the merits of the 

 question raised, this species is here left where Dr. Dawson first placed 

 it. It is in either case very probable that true members of the Helicidse 

 really did exist during the Coalmeasure epoch, contemporaneously with 

 the Pupida3 which are known to have existed then, and which are pres- 

 ently to be mentioned. Dawsonella meekii is represented on Plate 

 2 by copies of Professor Whitfield's figures. 



If Dawsonella should prove not to belong to the Helicidae, the earliest 

 examples of that family which are yet known to occur in North Ameri- 

 can strata are found in the Laramie Group. From the Judith Eiver 

 Laramie beds of the Upper Missouri region Meek & Hayden obtained 

 two species which are referred to this family. The first they described 



*Am. Jour. Sci., vol. xx (3), p. 411, figs. 10 and 11. 

 tAm. Jour. Conch., vol. vi, p. 315, pi. 13, fig. 9. 

 JAm. Jour. Sci., vol. iv (3), p. 88. 

 $ Am. Jour. Sci., vol. xx (3), p. 413. 

 || Am. Jour. Sci., vol. xxi (3), p. 127. 



