DOSSILS OF THE DEVONIAN. 



139 



Subgenus MARTINIA McCoy. 



Spirifera (Martinia) glabra Martin. 

 tor list of synonyms, see British Carboniferous Brachiopoda, Davidson, vol. ii, p. 59. 

 Spirifera M. glabra is mentioned by Mr. Davidson in his monograph of 

 the British Carboniferous Brachiopoda, p. 62, as occurring in Devonian rocks, 

 and he also states that he had specimens from the Devonian of Devonshire 

 which appeared undistinguishable from those in the Carboniferous limestone. 

 Before reading this observation we had compared the Devonian specimens 

 from Nevada with examples of S. (M.) glabra from the Carboniferous lime- 

 Stone of England, and also with Mr. Davidson's beautiful illustrations of the 

 species, and concluded that they were at the most but a variety of the same 

 species, and it is only for convenience in referring to the Nevada Devonian 

 form that a varietal name is proposed. 



Spirifera (M.) Franklini Meek, 1869 (Trans. Chicago Acad. Sci., vol. i, 

 p. 107, pi. xiv, fig. 12), is, as mentioned by Mr. Meek, closely related to S. 

 (M.} glabra, and with the original specimen before me to compare with the 

 Nevada shells and Mr. Davidson's figures of the species, it scarcely appears 

 to be more than a variety, if even that, of S. (M.) glabra. Mr. Meek sepa- 

 rated it from S. (M. ^glabra on account of having the lateral margins of the 

 area of the ventral valve extending out part way parallel to the hinge mar- 

 gins, instead of sloping regularly from the beak to the extremities of the 

 hinge. In the variety to be next described both characters occur on the 

 area of the ventral valve on different specimens, so that it is scarcely a 

 good specific distinction. 



Spirifera (M.) glabra, var. Nevadensis, n. var. 

 Plate iii, fig. 5 ; pi. xiv, figs. 14, 14 a, 6. 



The range of variation among the specimens in the collection is con- 

 siderable, as they differ in the strength and angularity of the mesial fold 

 and sinus, and the depression along the middle of the mesial fold of the 

 dorsal valve may be strong as in the example illustrated on plate xiv, fig. 

 14, or entirely absent even in large-sized specimens. Some shells are also 



