6o Journal of conchoLogV. 



PRELIMINARY REMARKS ON THE MOLLUSCAN 

 FAUNA OF COLORADO. 



By T. D. a. COCKERELL. 



Ever since July, 1887, 1 have had in preparation a detailed 

 list of the mollusca of Colorado, which, however, cannot yet be 

 considered complete, since records are still entirely lacking for 

 very many of the counties, and one or two questions of nomen- 

 clature still remain unsettled. It may therefore not be amiss to 

 offer a few preliminary remarks on the subject, leaving details 

 of precise localities, &c. to be given in the full list. 



Previous Records. — The foundation of Colorado Con- 

 chology was laid by E. Ingersoll, who enumerated some forty- 

 two species in a paper in Bull. U.S. Geol. Survey, 1875. Since 

 that date various notes and records have appeared, which, how- 

 ever, have not added greatly to our knowledge of the mollusca 

 of the State. These, together with Ingersoll's contributions, 

 bring the number of recorded species up to forty-eight, to 

 which I can now add eleven, making a total of fifty-nine. This 

 will seem an exceedingly small number to European Concholo- 

 gists ; but the paucity of species of mollusca is the most promi- 

 nent feature of this region as compared with the eastern states 

 and Europe. 



Characteristic Features. — Besides the paucity of species 

 there are other marked features, notably the great preponder- 

 ance of boreal types — no less than twenty-five of the fifty-nine 

 species being distinctly boreal — while several others approach 

 thereto. There is but one species of slug, but that is variable, 

 and was on this account divided into two by Ingersoll. Hyalina 

 is abundant, and Patiila well developed (though less so than in 

 Utah), but excepting these and species of Microphysa and 

 Vallonia there is not a single Helix— l\ie great groups Mesodon, 



J.C, vi., Jan., 1889, 



