The fauna cf tlic MaxvUlc Liinrstoiic. 379 



The plications and intervening spaces, when tlie surface is well 

 preserved, are marked by tine longitudinal lines, showing even 

 on partiallv exfoliated specimens, and are also crossed by still 

 finer transverse stri;e which undulate in crossing the plications, 

 and on perfectly preserved surfaces ai)])ear to he minutely setose 

 on their edges. 



"The species is extremely variable in its general outline, as 

 exhibited among the collections from all of the many localities 

 from which I have examined specimens, especially in the ex- 

 tension of the hinge-line, and the ])roportional width of the shell 

 below, and also in the prominence of the mesial fold ; but the 

 form of the plications and the character of those marking the 

 fold and sinus are usually the same in all; while the most con- 

 stant and persistent character, and one 1 have been able to 



Fig. II. — S't^irifer kcokiik. Pedicle valve. (After Whitfield.) The form 

 of this species varies greatly in the Maxville limestone. 



(^letect on specimens from almost every locality noticed, consists 

 of the minute structure of the surface. I have lately examined 

 a large number of examples from the limestones and sandstones 

 of the Coal ]\Iea.sures of Xew Mexico, which corre.spond ex- 

 actlv with those figured by I'rof. Marcou under the name S. 

 Rockxiiioiitaiia. and hnd tliem showing all the variations in form 

 noticed among the Keokuk. St. Louis. Chester and Coal Measure 

 limestones of Ohio and the West, and am thoroughly convinced 

 they cannot be separated, even as local varieties, with any degree 

 of safety or satisfaction [Whitfield. 1895]." 



In the above bibliography Weller's arrangement has ])een 

 followed, except for the listing of Herrick's .V. incrchrscciis, 

 which is undoubtedly tlie same as the other Maxville Sl^irifcrs. 

 Had the writer been bolder and followed his own inclinations, 



