DEVONIAN SPECIES. 43 



arcuace area, with nearly parallel margins. The beak of its ventral valve 



is also distinctly more incurved, as is that of its dorsal valve. It is likewise 



more nearly equivalve, has rather smaller and more numerous costse, while 



its mesial fold differs in being depressed and furrowed along its top, instead 



of rounded. 



Locality and position. — Treasure Hill, White Pine District, Nevada; 



from the dark Devonian limestone in which the White Pine Silver Mines 



occur. 



Spiripbr (Trigonotreta.) strigosus, Meek. 



Plate 3, figs. 5, 5 a, 5 6. 



Spirifera macra, Meek (1860), Proceed. Acad. Nat. Sci. Philad., XII, 309 (not Hall, 1856). 

 Spirifera sirigosa, Meek (1860), to extra copies of the above cited paper. 

 Spirifer strigosus, Meek (1876), in Col. Simpson's Eeport Expl. across the Great Basin 

 of Utah, 347., pi. 1, figs. 5, a, &, c, d.* 



Shell rather under medium size, moderately convex, subtrigonal, or 

 approaching subsemickcular, with the greatest breadth on the hinge-line; 

 lateral extremities generally more or less acutely angular; lateraPmargins 

 converging to the prominent, subangular middle of the front, with a some- 

 what straightened or convex outline. Dorsal valve convex in the middle, 

 and compressed toward the lateral extremities; mesial fold narrow, rather 

 prominent, and sometimes subangular near the front, continued to the beak. 

 Ventral valve scarcely more convex than the dorsal, most gibbous in the 

 umbonal region, with convex lateral slopes; beak moderately prominent, 

 ' and distinctly incurved; area rather nan-ow, well defined, and narrow- 

 ing off laterally, so as not quite to reach the extremities of the hinge, 

 arched, and directed obliquely backward with the beak, rather distinctly 

 striated vertically; mesial sinus corresponding in size to the fold of the other 

 valve, the margins of both being usually a little produced in front, so as to 

 impart an angularity to the outline of the middle of the anterior margin. 

 Surface of each valve ornamented with from twenty to about twenty-six 

 radiating costse (counting at the free margins), some of which are simple, 

 while others bifurcate. Of these costse, about six or seven usually occupy 

 the mesial fold and sinus. Two or three of those within each margin of 



* I add references to Capt. Simpson's report here, in reading the proofs, that rei>ort 

 having been published since the revision of this. 



