258 FAL.1^:ONTOLOGY. 



The spocimc^ns of this species seen are iiiosth' poor; one, however, pre- 

 serves the t'urni and t'eatiuvs, witli hut htth' or no distortion, giving the 

 characters as ah()\e. The shell vai'ies considerable from the description of 

 Dr. C. A. White ; l)ut, on comparison with a group of several individvials 

 from the typical local it\', sent hv Dr. White as of that species, we find the 

 variations great enough to include sj)ecimens departing still further than 

 these here referred. 'J'lie minute surface-structure having pustules has not 

 been observed among thost- in this collection, as they are all more or less 

 exfoliated, and it does not appear to be commonly preserved on those from 

 the typical locality. The greater number of plications would seem to be 

 a distinguishing feature, but eight of the twenty-two counted occur on the 

 cardinal slopes, where, in very many cases, they might not be distinguish- 

 able. 



Formation (Did localiti/. — In limestone of the Waverly group, at Logan 

 Cation, Wahsatch Range, Utah. Collected by S. F. Emmons, esq. 



Genus TEREBliA^rULA (Llhwyd.) Brug. 

 Tekkbratula Utah n. sp. 



I'late IV, iig. 18. 



Shell of medium size, elongate- ovate, the greatest width opposite the 

 middle of the dorsal valve, forward of which point the sides are somewhat 

 rapidly contracted to the rather squarely truncated front mai'gin. Valves 

 ventricose, the ventral more gibbous than the opposite. Dorsal valve most 

 ventricose within the upjjer third of the valve ; beak small and sharplj^ 

 pointed for a dorsal beak, scarcely if at all incurved. Surface of the shell 

 smooth, with the exception of several ratiier strong concentric lines marking 

 stages of growth. Beak of ventral valve not observed. 



The shell is described from a separate dorsal valve and a partially con- 

 cealed ventral valve, but the form of the shell is somewhat different, and 

 the proportions unlike any other known from rocks of a corresponding age. 



Formation and localiti/. — From a dark limestone of Lower Carboniferous 

 age (Waverly?), on the Cottonwood divide, 800 feet east of Reed and Ben- 

 son's mine, Wahsatch Range, I 'tali. Collected by J. E. Clayton. 



