90 SUBCARBONn-EROUS PERIOD. 



In tlie course of some extended remarks upon tlie genus Spirifer, 

 Messrs. Meek and Worthen (Geological Survey of Illinois, vol. iii, 532) 

 have shown tliat the oiiginal species of the genus jiossessed the same 

 peculiarities of structure that formed the basis of Professor Winchell's genus 

 Syrinriothyris. They also show that the numerous species which have been 

 generally regarded as typical fomis of the genus Spirifer really belong to a 

 group for which Koenig proposed the generic name of Trigonotreta long 

 before the publication of Syringothjris. This being the case, a strict enforce- 

 ment of the rule of priority in scientific nomenclature will require that 

 Syringothyris be suppressed, and that all shells having the stnicture which 

 characterizes that group retain the name of Spirifer ; also that Koenig's 

 name Trigonotreta be applied exclusively to those ordinary fomis which 

 have so generally been refen-ed to Spirifer, at least in a subgeneric sense. 

 In view of the question thus raised, and being at present without the means 

 of deciding it for myself by personal investigation, the generic assignments 

 I have made of these forms in tliis report should be regarded as provisional 

 only. 



Position and locality. — Strata of the Svibcarboniferous period ; Mountain 

 Spring, old Mormon road, Nevada. 



Subgenus MAETINIA McCoy, 1844. 



Spirifer (Martinia) peculiaris Sliumartl. 

 Plato V, fig. 7 a aud 6. 

 Spirifer peculiar k Sliuiuard, 1855, Geological Survey of Missouri, part 2, 202. 



Ventral valve arching regularly from beak to front, the curvature being 

 gi'eatest near the beak ; sides convex ; beak nan*ow, extended, incurved ; 

 antero-lateral margins broadly rounded ; postero-lateral margins abruptly 

 rounded to the short hinge-line; postero-lateral surfaces rounded backward to 

 the small, indistinctly-defined cardinal area; foramen triangular, its apical end 

 closed by a pseudo-deltidium ; mesial sinus shallow, traceable nearly to the 

 beak, widening a little more rapidly near the front than elsewhere, nearly 

 plain, but two faint, incipient plications are observable, one at each side, 

 and also a slight flattening along its middle. Surface on each side of the 

 sinus marked ]>y six or seven small, convex-flattened plications, which are 



