GASTEROPODA. 43 



of the volution. On well preserved specimens the striae are sharply 

 elevated, but are subject to considerable variation which may be due to 

 erosion or maceration before imbedding. 



A critical comparison of specimens originally referred to this species has 

 led to the conclusion that some of them should be separated, and the specific 

 term restricted in its application to such forms as are here illustrated. 



Formation and localities. In limestone of the Upper Helderberg group, near 

 Columbus, Ohio, and in some doubtful specimens from Genesee and Erie 

 counties, N. Y. 



LOXONEMA PEXATA Var. OBSOLETA. 



PLATE XIII, FIG. 13. 

 L'jxoneina pexata var. obsolete, Hall. Illustrations of Devonian Fossils: Gasteropoda, pi. 13. 1876. 



The specimen figured retains a part of three volutions — the last nearly entire. 

 The form is the same as in typical specimens of L. pexata. The surface is 

 marked by obscure or obsolete striae, which condition may be due to age or to 

 maceration and erosion before imbedding. 



Formation and localities. In limestone of the Upper Helderberg group, t at 



quarries north of Columbus, Ohio. 



% 



LOXONEMA SICTJLA n. sp. 



J'l.ATE XXVI, FIG. 1. 



SHELL small, slender, very gradually enlarging from the apex. Volutions short 

 and moderately convex; fourteen in an entire specimen of seven-eighths 

 of an inch in length ; a narrow, flattened space at the upper margin of 

 each one, which is limited below by an undefined line parallel to the suture. 

 SuEFACl marked by comparatively strong and coarse elevated striae, which 

 curve gently backward from the suture to the middle, and thence forward 

 to the base of the volution. 

 / rmation and locality. In decomposing chert of the Upper Helderberg lime- 

 stone, near Jamesville, Onondaga county, N. Y. 



