70 Dr. VT. B. Carpenter on the Shell-structure of 



projecting into the interior of the shell. Tliis peculiarity not 

 being indicated by any corresponding peculiarity of external 

 conformation, shells which are now found to present it have 

 been ranked among Spirifers by our very highest authorities'*^. 



2. Chips of the shells which have been ranked by American 

 palaeontologists as Spirifer cuspidatus and Sp. subcuspidafus. 



3. Chips of the shell referred to by Mr. Meek as having been 

 sent to Mr. AVorthen by ]Mr. Davidson as a typical specimen of 

 Spirifer cuspidatus from Millecent in Ireland. 



In all the foregoing- specimens the shell-structure was ex- 

 tremely well preserved. 



Through the kindness of Mr. Jukes, who sent a collector to 

 Millecent on purpose to obtain for me specimens of the last- 

 mentioned type, I have also been enabled to examine — 



4. Two entire specimens of reputed Spirifer cuspidatus from 

 Millecent. Although there was but little shell on these speci- 

 mens,, that little was well preserved, and proved quite sufficient 

 for my requirements. 



Finally, the readiness of Mr. Davidson to make any needful 

 sacrifice for the sake of arriving at the whole truth on this point 

 has led him to place at my disposal — 



0. The entire specimen of Spirifer cuspidatus from Millecent, 

 figured by him in his ' Carboniferous Brachiopoda ' i plate 8. 

 fig. 19) as a typical representative of the species. The shell of 

 this specimen is so well preserved that lamellse scaled oif from 

 it could scarcely be distinguished from those of a recent Bhyn- 

 chonella. 



All the foregoing specimens have been examined under mag- 

 nifying-powers of from 50 to 100 diameters, (1) by mounting 

 in Canada balsam such lamellae as were already thin enough to 

 be transparent, and \2': by grinding down such chips as were 

 originally opaque until they became thin enough to be seen 

 through, and then mounting them in Canada balsam. This is 

 the method which I have uniformly practised, when able to do 

 so, in the examination of the shells of fossil Brachiopoda ; and 

 I consider it the only one by which satisfactory results can be 

 obtained. A natural lamella gives the structure of that parti- 

 cular layer of which it formed part, whilst a thin section procured 

 by grinding will generally traverse all the layers of the shell. 

 The following are the facts thus revealed as to the structure of 

 the specimens just enumerated : — 



1. The type-specimen of Prof. Winchell's Syringothyris ex- 

 hibits distinct perforations of about 1 -3000th of an inch in 

 diameter, set at an average distance of about l-300th of an 



• A fully illustrated description of this genus, by Mr. Davidson, will be 

 found in the ensuing i^ July) Number of the Geological Magazine. 



