84 PALEONTOLOGY. 



as from the other fossils found in the same beds, I can scarcely doubt that 

 this South American shell is really identical with A. siibtilita.^ 



Although the figure given in the Journal of Science by Shephard, of 

 the shell described by him in 1838 under the name Terebratula argentea, 

 does not resemble adult forms of A. suhtiUta, I have long suspected that it 

 represents an immature example of this species, as no other similar form is 

 known among all the numerous specimens from our western Coal-Measures. 

 If it should be found to be the same, Shephard's specific name would have 

 to stand, as it has priority of date. 



Locality/ and position.— Jluhj Group; Moleen Peak; near Humboldt 

 River, and other Nevada localities, in a light-colored limestone. 



Genus SPIRIFERINA, d'Orbigny. 

 Spiriferina (undt. sp.). 



Plate 8, figs. 5, 5 a, 5 6. 



Compare Spirifer octopUcatus, Sowerby (1827), Miii. Conch., V, 120, pi. 662, figs. 2, 3, 

 and 4 (= Spiriferina cristata var. octopUcata of Davidson and others). 



Shell rather small, very gibbous, about equivalve, subtrigonal or 

 rhombic-subquadrangular in general outline; hinge-line apparently equal- 

 ing the greatest breadth. Ventral valve most convex in the umbonal region; 

 beak incurved and projecting backward; mesial sinus narrow, well defined, 

 somewhat flattened, and, without costse within, continued to the point of 

 the beak, and having its anterior margin produced forward in the form of a 

 somewhat angular projection fitting into a corresponding sinus in the margin 

 of the other valve; lateral slopes with each five to six elevated, simple, 

 narrowly-rounded, or subangular costse of the same size as the deep depres- 

 sions between ; cardinal area of moderate height, with well-defined margins 

 that slope from the beak apparently to the lateral extremities of the hinge, 

 rather strongly arched, and inclined obliquely backward. Dorsal valve with 

 a narrow, very prominent, subangular, simple mesial fold, most elevated at 

 or near the front, but continued to the beak, and projecting forward so as 

 to give a rather acutely angular character to the outline of anterior margin ; 



♦Since this was written, Professor Derby, of Cornell University, has identified A. 

 subtilita from Brazil (see Bull. Cornell University, I, No. 2, 7.) 



