258 PALEONTOLOGY. 



The specimens of this species seen are mostly poor ; one, however, pre- 

 serves the form and featm-es, witli but little or no distortion, giving the 

 characters as above. The shell varies considerable from the description of 

 Dr. C. A. White ; but, on comparison with a group of several individuals 

 from tlie typical locality, sent by Dr. White as of that species, we find the 

 variations great enough to include specimens departing still further than 

 these here referred. The minute surface-structure having pustules has not 

 been observed among those 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 grenter 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 and locality. — In limestone of the Waverly group, at Logan 

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



Genus TEREBRATULA (Llhwyd.) Brug. 

 Terebratula Utah n. sp. 



Pliite IV, fig. 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 margin. Valves 

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

 ventricose within the upper third of the valve ; beak small and sharply 

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

 smooth, with the exception of several rather 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 locality. — 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, Utah. Collected by J. E. Clayton. 



