LOWER CARBONIFEROUS FOSSILS. 539 



Camarotcechia herrickana ii. sp. 

 PI. LXIX, figs. 2a, 2b, 2c. 



Ventral valve rather shallow, most prominent a little behind the mid- 

 dle, flattened in front and at the sides. Outline nearly that of a square. 

 Sinus shallow, beginning near the middle of the shell; marked by two 

 strong plications, on either side of which are five or six others slightly finer. 



Dorsal valve considerably wider than long, sectoriform, more gibbous 

 than the ventral; sides reflexed. Fold not very high, marked by three 

 strong angular plications. On either side are five plications, the more 

 lateral tvvo smaller than the others. 



This species occurs in about the same beds as C. metallka, but is sel- 

 dom associated with it at the same locality. It is readily distinguished 

 from G. metallka by its somewhat large size, less strong fold and sinus, 

 and coarser and less numerous plications. Of these, C. metallka has five 

 on the fold and eight on either side, while C. herrickana has but three on 

 the fold and five on each side. 



Tins species has not been observed with the two valves in conjunction, 

 but it seems to have been a much less inflated form. 



It is possible that this species might correctly be referred to some one 

 of the numerous Rhynchonellids described from the Marshall group by 

 Winchell. I have studied his descriptions with care, but none cover the 

 characters of this form sufficiently closely to warrant an identification in 

 default of both illustrations and identified material. 



Length of a single ventral valve, 10.5 mm.; width, 12 mm. Length 

 of a separate dorsal valve, 8.5 mm.; width, 10.5 mm. 



This same form, or one probably only varietally distinct from it, is 

 found at Pellas, Marion County, Iowa. 



Formation and locality: Madison limestone, limestone bluff north of 

 Little Sunlight Creek, Absaroka Range, 600 feet above the stream; Arnold 

 Hague. Divide between Gallatin River and Panther Creek, Gallatin Range; 

 amphitheater east of Bannock Peak, Gallatin Range, bed 28; "W. H. Weed. 

 Crowfoot Ridge, Gallatin Range, top of bed 26, upper part of bed 27, bed 

 28; J. P. Iddings and W. H. Weed. North end of Teton Range, north of 

 Owl Creek; W. H. Weed. Chouteau limestone, Pellas, Marion County, 

 Iowa. 



