10 THE GASTROPOD GENUS YVANIA 



of the suture" although this character is nowhere mentioned in his descriptions. 

 Because my Coal Measures species possess these two unusual characters in 

 common with de Koninck's Belgian forms, I confidently place them in the 

 same genus which is here emended as follows : 



s y 



Genus YVANIA Bayle emend. Weller 



Description. — Pleurotomariidae, medium to fairly high spired, subtrochi- 

 form to turreted : mature whorls with one or two> sharp lateral angles — if only 

 one angle the whorl has a strongly convex hasal portion. Slit band prominent, 

 situated on the upper slope of the whorl just above the upper lateral angle, 

 flat or slightly concave, sharply bounded upon each side by raised costae. 

 Aperture, as shown by the lines of growth, convex between the slit and suture, 

 linguliform, extending backward near the suture and meeting it at an angle 

 acute in a backward direction or producing a shallow concave sinus ; on the 

 side below the slit band, strongly convex ; on the base more or less broadly 

 concave. Columellar lip somewhat thickened and recurved, umbilicus small 

 or closed, no callosity on the inner lip. Surface ornamented by more or less 

 numerous revolving costae which may or may not be raised slightly at inter- 

 vals to give a nodose appearance, especially adjacent to the suture. Lines 

 of growth faint, rarely observed on some species- 



This genus differs from all other angulated Carboniferous Pleuroto- 

 mariidae in possessing a slit band situated upon the upper slope of the whorl, 

 and by the form of the aperture which extends backward adjacent to the 

 suture. 



Genus HYPSELENTOMA Weller, n. gen. 



The only other angulated Carboniferous species known to me which 

 possess a band upon the upper slope of the whorl are Pleurotomaria hcr- 

 humerosa and P. inornata Meek, possibly P. humerosa Meek and Hayden, 

 and an undescribed form from the Graham formation of Texas. These 

 differ from Yvania in not possessing a true slit, the band being simply the 

 band of the sinus, and also in the forward direction of the lines of growth 

 as the suture is approached. These forms constitute a well defined and 

 easily distinguished group. It is my desire to establish it as of generic rank, 

 and I propose for it the name Hypsclcntoma' and select P. perhwnerosa as 

 the type. 



c Op. cit., pi. 27, fig. 5. 



7 Wn^os, high up; kvTotxii, incision. 



