BRITISH SILURIAN BRACHIOPODA. 95 



Prom the identity of external shape presented by Prof. Hall's Meristina Maria with 

 Dalman's Atrypa tumida Mr. Glass and myself felt that with such similar exteriors it was 

 hardly possible to believe they could be possessed of dissimilar interiors. At my request, 

 Prof. Hall kindly sent me several examples of his Meristina Maria that Mr, Glass might be 

 able to develop their interior arrangements, this he effected with his usual ability, 

 and was soon able to show that the so-called Meristina Maria presented the forked 

 character of the loop of Meristella tumida. Under such circumstances, it became necessary 

 to remove Meristina Maria from the genus Meristina, and to place it among the 

 synonyms of Whitfieldia tumida} 



Through Mr. Whitfield's kindness we have also been able to examine the prepared 

 specimen of Meristina Maria from which the figure at p. 299 of the ' Palaeontology of New 

 York ' was made, and Mr. Glass soon perceived that Mr. Whitfield had unfortunately 

 destroyed the bifurcating lines at the end of the loop in making a perforation under the 

 beak of the ventral valve, and that this had led to the mistake in Prof. Hall's figure. 



Through the kindness of Mr. Whitfield we have been able to examine the admirable 

 preparations made by himself qI Meristina nitida, Hall; and these agree with the description 

 given of the genus Meristina by Prof. Hall, and have the lamellae of their spires united 

 by a simple loop. This species should consequently be considered as the type of the 

 genus Meristina. 



I was, however, in error when, at p. 114 of my ' Silurian Monograph,' I considered 

 Sowerby's Terehratula Iceviuscula to be a synonym of Hall's Meristella nitida ; for, although 

 Mr. Glass has not been able to completely develop the connecting processes of Sowerby's 

 shell, still he has seen enough of it to lead him to believe that it was not possessed of a 

 simple loop, as in M. nitida. It will, however, remain to be determined whether Hall's 

 AI. 7iitida is specifically distinct from Dalman's Terehratula didyma. I believe them to 

 belong to the same species ; and Dalman's name is the oldest. 



The Terehratula didyma of Dalman is decidedly referable to Meristina, and should be 

 the type of the genus. An English specimen from the Wenlock Limestone of Lincoln Hill, 

 Shropshire, successfully developed by Mr. Glass, shows the simple loop of Meristina. 



Several Swedish specimens of Dalman's T. didyma having been sent kindly to me by 

 Prof. Lindstrom, of Stockholm, Mr. Glass has been able to develop the simple loop in 

 them also, and in the most complete and satisfactory manner. 



It will remain a question for further consideration whether we are justified in 

 retaining the three distinct generic denominations of Nucleospira, Betzia, and Meristina, 

 for shells possessing the same simple loop. The only differences between them is to be 



1 Mr R. P. Whitfield writes me, on 25th of April, 1881 : "There has always been some doubt in 

 regard to the absolute generic identity of Meristina nitida and M. Maria, not on account of the difference 

 of the loop, for I know of none, as you will see from the specimen sent, but on account of the perforation 

 of the apex of M. nitida, which does not occur in M. Maria, and I think Prof. Hall always looked upon 

 Meristina nitida as the type of Meristina.''' 



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