55° 



GEORGE H. GIRTY 



best be seen. It is doubtful, however, whether these can be attrib- 

 uted to normal costation, which ought to be still better exhibited 

 toward the front, rather than to inequalities in the rapidly thinning 

 apical callosity, such as would be shown on the inside but not on 

 the outside of the shell. Similar markings have been observed 

 on other species of Syringothyris. 



S. randalli occurs at the locality and horizon of the classic 

 association of Syringothyris with Spirijer disjunctus. 1 S. dis- 

 junctus, or a species closely allied to it, occurs in equal abundance 

 with the Syringothyris. Superficially the two types are distin- 

 guished by the fact that one has a simple fold and sinus and the 

 other is plicated. Where this character is obscured, internal molds 

 of ventral valves might be confused on casual observation, although 

 one type possesses the syrinx and the other does not, and from the 

 evidence in hand it seems almost certain that Simpson did thus 

 confuse them, since one of the three type specimens of Syringothy- 

 ris randalli, all of which are internal molds of ventral valves, is 

 clearly a Spirifer. Although it does not show any surface char- 

 acters whatever, it has the internal characters of and almost cer- 

 tainly belongs to the form commonly referred to Spirifer disjunctus 

 in the Warren area. It appears plausible, therefore, that Simpson 

 confused these two forms, and seeing well-marked plications on the 

 fold and sinus of some specimens (S. disjunctus) felt justified in 

 putting them into his description and into his figure, although 

 they are only faintly suggested in the specimen from which the latter 

 was drawn. Conclusive evidence can come only through an 

 examination of the external mold of the type specimen, which is, 

 of course, impossible; or less adequately through the discovery 

 of other specimens unmistakably possessing the characters which 

 S. randalli is said to have. But, for my own part, I am fairly 

 satisfied that S. randalli is conspecific with the abundant asso- 

 ciated Syringothyris which clearly has a simple fold and sinus. 



Granting, however, that S. randalli does possess the plicated fold 

 and sinus ascribed to it, let us examine into the argument by which 

 this character is thought to justify the erection of a new genus. 



1 At Warren, Pa., at a horizon not far below the "Sub-Olean conglomerate" 

 in a series of strata which I at one time proposed to call the Bradfordian group. 



