LOWER CARBONIFEROUS FOSSILS. 533 



the citations in this country have been from the Coal Measures. Norwood 

 and Pratt en, however, have identified this species from the "Mountain lime- 

 stone" of Paris, Missouri. 



Formation and locality: Madison limestone, east side of Gallatin River, 

 west of Electric Peak; Crowfoot Ridge, Gallatin Range, top of bed 25, top 

 of bed 26 ; J. P. Iddings and W. H. Weed. North side of north fork of Mill 

 Creek, Snowy Range ; Louis V. Pirsson. 



Productus gallatinensis n. sp. 

 PI. LXVIII, figs. 11«, lib, lie, lit?, la, lb, 1c. 



Dorsal valve not known. Ventral valve small, strongly arched, the 

 curves on either side of the most elevated point being nearly alike. Beak 

 small, rapidly expanding, produced, so that the small distinct ears occur 

 about one-third the shell length in front of the apex. Top of the shell 

 broad, flattened, but not sinuate; sides nearly plain and vertical. The 

 width slightly exceeds the greatest length, and is about one and one-half 

 times the height. The visceral region is marked by numerous distinct con- 

 centric wrinkles, and the shell is ornamented with fine, straight, radiating 

 stria? which bifurcate on the anterior portion. A few large spine bases 

 can be seen on the anterior portion of the shell. 



Figs, la, lb, 1c, of PI. LXVIII, represent a form which was at first 

 identified as Productella arcuata Hall, but which I now regard as only a 

 variety of P. gallatinensis. It is represented from only one locality, the 

 top of bed 25, Crowfoot Ridge, Gallatin Range, and is there found asso- 

 ciated with true P. gallatinensis. The shape is narrower and more elongate, 

 while the striae have not the even, rigid, wirelike appearance characteristic 

 of the latter. It differs from P. arcuata in having the striae finer and more 

 regular and strong. 



The relations of P. gallatinensis, P. parviformis, and P. semireticulatus 

 are close, and I am almost disposed to regard them as only varieties of 

 the same type. P. gallatinensis is smaller than P. semireticulatus, more 

 arched, finer striated, narrower, and with more vertical sides. However, 

 some of the variations of either type approach each other closer than the 

 figured specimens would indicate. Still more nearly related to the species 

 under discussion is P. parviformis. In shape the latter appears to be a 

 miniature reproduction of P. gallatinensis, but the surface ornamentation is 

 of about the same fineness. 



