NATURAL SCIENCES OF PHILADELPHIA. 275 



Observations on the Microscopic Shell Structure of SPIRIFER CUSPIDATUS, 



Sowerby, and some similar American forms. 



BY F. B. MEEK. 



In his valuable and accurately illustrated work on the British Carboniferous 

 Brachiopoda, page 45, Mr. Davidson states that Spirifer cuspidatus, Sowerby, 

 "belongs to the genus Spirifer proper, and not to the subgenus Cyrtia," as 

 he and others had supposed. He also adds that " no specimen of S. cuspi- 

 datus I have hitherto been able to examine, has exhibited a deltidium in its 

 entire condition, but which, in all probability, was not perforated by a circu- 

 lar foramen, as seen in true types of the subgenus Cyrtia." In a note at the 

 bottom of the page containing his explanations of plate viii., however, of the 

 same work, he corrects the above statement as follows : " At page 45, I stated 

 that no specimen of S. cuspidatus I had hitherto been able to examine pos- 

 sessed its deltidium, and that I considered it was, in all probability, pot per- 

 forated by a circular foramen, as in the true types of the subgenus Cyrtia. 

 Subsequently, however, Mr. S. P. Woodward showed me the internal cast of 

 the ventral valve of a specimen in the British Museum, thought to have be- 

 longed to S. cuspidatus, and derived from the Dolomitic carboniferous lime- 

 stone of Bredon Hill, in which there is evidence that the deltidium was in 

 reality perforated by a circular foramen as in Cyrtia." Of this internal cast, 

 as well as of a gutta-percha mould made from it, Mr. Davidson gives good 

 figures, on plate ix. (figs. 1 and la) of the work above cited. 



From these remarks, and the accompanying figures, it seemed to be nearly 

 or quite demonstrated, that S. cuspidatus is a true Cyrtia, as had formerly 

 been supposed by Prof. McCoy and Mr. Davidson, and, as it is also the type 

 upon which Sowerby had founded his older genus Spirifer, it would follow, 

 as a matter of course, that Cyrtia, Dalman, could only be regarded as an exact 

 synonym of the typical section of Spirifer, Sowerby, which view was adopted in 

 the work on the Palaeontology of the Upper Missouri, by the writer and Dr. Hay- 

 den. It will also be observed that the shell structure of Spirifer is there de- 

 scribed as being impunctate, in accordance with the views of Dr. Carpenter 

 and Mr. Davidson in regard to the group to which we propose to restrict it, 

 after separating, generically, the punctate types Spiriferina and Cyrtina. 



Some examinations I have recently had an opportunity to make, however, 

 of the shell structure and internal characters of several American forms, 

 closely allied to, if not in some instances identical with, Spirifer cuspidatus, 

 as well as of a supposed authentic British example of that species, in the 

 collection of Mr. Worthen, at Springfield, have given rise to doubts in regard 

 to the correctness of some of these conclusions. 



I was led to make these examinations by observing in Mr. Worthen's col- 

 lection excellent specimens, apparently of Spirifer capax, Hall, (very similar 

 to S. cuspidatus, Sowerby) from Clarksville, Missouri, showing exactly tho 

 form and internal characters of a genus Syringothyris, proposed by Prof. 

 Winchell, in the Proceedings of the Academy for January, 1863. It will be 

 remembered that Prof. W. described the type of this genus as having the 

 form and general external characters of Spirifer cuspidatus, but differing in 

 the possession of a curious internal tube connected with the inner side of a 

 kind of deep-seated, false deltidium, or transverse plate passing across be- 

 tween the dental laminae. He also states that the shell structure is impunctate. 



On examining the specimens above alluded to in Mr. Worthen's collection, 

 I at once observed their exact agreement in all internal characters, as well as 

 iu the form, ornamentation, &o., with Syringothyris, but soon saw, while look- 

 ing at them with a gool pocket lens, some evidences of a punctate structure, 

 and, on afterwards placing fragments of the shell under a high magnifier, 

 where they could be examined by transmitted light, they were found to be 

 beyond doubt punctate. Subsequently I mentioned this fact to Prof. Win- 



1865.] 



