216 ANNALS NEW YORK ACADEMY OF SCIENCES 



1903. Productus inflatus (non McChesney). Girty, U. S. Geol. Survey, Prof. 



Paper 16, p. 359, pi. 3, fig. 1-16, 2, 2a, 3. - 

 Hermosa formation: San Juan region and Ouray, Colorado. 

 Weber limestone : Crested Butte and Leadville districts, Colorado. 

 Carboniferous: Glenwood Springs, Colorado. 



1904. Productus inflatus ? (non McChesney). Girty, U. S. Geol. Survey, Prof. 



Paper 21. p. 52, pi. 11, figs. 5. 6. 

 Pennsylvanian (Naco limestone) : Bisbee quadrangle, Arizona. 



In 1903, I referred to McChesney's P. inflatus a group of shells from 

 the Pennsylvanian of Colorado, expressing at the time a certain doubt 

 whether they were actually identical with it. For this gi'oup I would 

 now suggest the varietal name coloradoensis. The western variety is of 

 different geological age and associated with a very different fauna from 

 typical Productus inflatus. Intrmsically it is larger and broader and 

 marked by much larger spines. 



The Arkansas shells provisionally referred to the same variety are as- 

 sociated with P. inflatus in the Fayetteville shale and probably inter- 

 graduate with it. They are chiefly distinguished by being larger and 

 broader, though, as the specimens thus far obtained are neither numerous 

 nor perfect, other differences may develop with closer knowledge. I have 

 observed, upon most of the specimens sufficiently preserved to show this 

 character, a diagonal line of spines about where the ear may be said to 

 join the body of the shell. This feature occurs in P. inflatus rarely, if 

 at all, but I have called attention to a similar thing in Productus senii- 

 reticulatus var. animasensis. There are few specimens about which one 

 would hesitate whether to refer them to P. inflatus or to P. inflatus var. 

 coloradoensis, and perhaps there would be fewer still if the specimens 

 themselves were more perfect. 



These Arkansas shells simulate typical P. inflatus var. coloradoensis 

 rather closely. Much of the Arkansas material is broken or exfoliated, 

 but I believe it does not have as numerous or as large spines as that from 

 Colorado. The sinus is also deeper. 



Productus arkansanus sp. nov. 



The shells included under this title present so many variations that 

 it is difficult to frame a general description of them. They attain a size 

 which may be called medium or even rather large, but many of the 

 specimens actually bandied are small. In the young (small) stages, the 

 shape is subquadrate and rather transverse, while in a mature condition, 

 the length is sometimes greater than the breadth. Nevertheless, the 

 transverse shape is in certain instances retained to the mature condition, 

 while, on the other hand, the tendency to elongate is sometimes mani- 



