DESCRIPTIONS OP SPECIES. 359 



Productus spwalis Waagen, from India, and to ProdMctus ioliviensis d'Orbigny, but 

 is clearly distinct from either. It is also very closelj" allied to the form I have 

 designated as P. inflatihs McChesney, which is little more than a variety, and the 

 two apparently intergrade completely. This statement, however, might have to be 

 modified if all the material were in perfect preservation. 



In its typical condition Productios semireticulyatus var. hermosanus is largely 

 confined in Colorado to the San Juan region. The stations at which well character- 

 ized material has been obtained are, in the San Juan region, 2204, 2207, 2210, 2236, 

 2241, 2243, 2302, 2331, 2333, 2335, in the Leadville region, 2262, and in the Crested 

 Butte, 2245 and 2293. Most of the other identifications rest upon intermediate 

 gi-adations between it and P. Inflatus, or upon imperfect and scanty material. In 

 the San Juan region the two forms seem to be well distinguished and it is in other 

 areas where P. imflatus is the prevailing form that intei'mediates mostly occur. 

 P. infiatus displays more of a tendency to graduate into P. sem.ireticulatus var. 

 hermosanits, than into P. mfntic-s, and in some cases the coarser forms of P. inflafus 

 when associated with the finely striated variety have been placed with P. seinireticu- 

 latus var. liermosamm when, had they been found alone, they might have been 

 referred to the>other. 



This species also occurs in the Mississippi Valley, where its horizon seems to be 

 at the base of and just below the Upper Coal Measures of the Kansas section. It 

 thus is an earlier form than the typical, or at all events the best-known, variety of 

 P. semiretieulatus, and is probably its progenitor. The latter is as yet not known to 

 occur in Colorado. 



The identification of this form in the fauna from Sinbads Valley is doubtful. 



Locality and horizon.— 'S>?i\\ Juan region (stations 2200, 2204, 2207, 2210, 2226?, 

 2236, 2241, 2243, 2331, 2333, 2334, 2335); middle and upper portions of the Hermosa 

 formation. Crested Butte district (stations 2245, 2291, 2293, 2300, 2302, 2304); 

 Maroon formation. Leadville district (stations 2252, 2259, 2262, 2264, 2265, 2266, 

 2275); lower, middle, and upper portions of the Weber formation. Oura}^ (station 

 2194); Hermosa formation. Dolores River region, Sinbads Valley (station 2285); 

 top of the Hermosa formation. 



pRODUCTUS INFLATUS McChesuej'. 



PL III, figs. 1 to lb, 2, 2a, 3. 

 1860. Productm infiatus. McChesney, Desc. New Spec. Pal. Foss., p. 40. 



Carboniferous limestone: Leavenworth, Ind. 

 1865. Produdus ivfiahis. McChesney, Illustrations New Spec. Foss., pi. 6, figs. la-c. 

 1868. Productm inflaiiis. McChesney, Chicago Acad. Sci., Trans., vol. 1, p. 27, pi. 6, figs. la-c. 



Carboniferous limestone: Leavenworth, Ind. 



Shell of medium size, very gibbous, transversely subquadrate. Ventral valve 

 highly inflated, the posterior' portion being more strongly flexed than the anterior. 



