DESCEIPTIONS OF SPECIES. 379 



reality. It is unusual for two species to be associated in the collection from a single 

 station, and even a certain amount of individuality is manifested in the different 

 areas represented in our collections. 



The discussion of this species opens with the citation of the original reference 

 of Margvnifera waihashensis, which is a sort of contradiction, since I do not consider 

 the form in hand quite the same as Norwood and Pratten's species. The uncertainty' 

 I am under regarding- their true relations must explain this action. 



Locality and ho7'izon.—'6&n Juan region (stations 2196, 2197, 2198, 2220, 2323); 

 lower and middle portions of the Hermosa formation. Crested Butte district 

 (stations 2302, 2.303, 2306, 2316); Weber limestone and Maroon formation. 



Maeginifeea ingkata n. sp. 



PL V, figs. 12, 12a, 13, 13b. 



?1875. Prodiictus lonffispinm. White (non Sowerby), (pars) U. S. Geog. Geol. Surv. W. 100th Mer., 

 Eept., vol. 4, p. 118, pi. 8, figs. 5c, d (not figs. 5a, b), (imprint of entire volume 1877). 

 Garl)oniferous: East of Minersville and at Meadow Creek, south of Fillmore, Utah; Camp Cot- 

 tonwood, Old Mormon road, Lincoln County, Nev. ; near Santa Fe, N. Max. 

 ?1877. Produclus longispinux. Meek (non Sowerby), U. S. Geol. Expl. 40th Par., Rept., vol. 4, p. 78, 

 pi. 8, figs. 4, 4a. 

 Carboniferous limestone: Fossil Hill, White Pine district, Nevada. 



I am uncertain of the specific relationships of this little shell and of the impor- 

 tance which should be attached to the characters which I am about to recount. 

 Because of the former consideration, 1 have decided to describe it as a new species, 

 and because of the latter I do so with some misgivings. The form which I shall take 

 as my type is found in great abundance at station 2259 in the Leadville region-; but it 

 occurs there only in the condition of casts. It is small, transverse, subrectangular. 

 A transverse diameter of 1.5 mm. and a longitudinal of 11 mm. is somewhat above the 

 average. The curvature is strong, the ears distinct, large, quadrate, and somewhat 

 upturned. The surface is marked by strong, moderately fine strife, about 7 in the 

 space of 5 mm., and by fine, regular concentric wrinkles over the posterior half of the 

 shell. The spines are small and rather numerovis. Mesial .sinus absent. Submar- 

 ginal ridges persistently well developed. 



This species can be distinguished from M. wabashensis var. by reason of the 

 strength of its strite and concentric wrinkles, its lack of a mesial sinus, and its I'egu- 

 lar instead of geniculate curvature. 



From 3L murieata it can be distinguished by being smaller, with larger, more 

 distinct ears, finer striae, and much fewer spines. 



The features mentioned in the description, especially the strong wrinkles and 

 stria?, conjoined with the absence of a sinus are relied on to distinguish this form 

 from the other American species. 



