70 Dr. W. B. Carpenter on the Shell-structure of 
projecting into the interior of the shell. This 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 
paleontologists as Spirifer cuspidatus and Sp. subcuspidatus. 
3. Chips of the shell referred to by Mr. Meek as having been 
sent to Mr. Worthen 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— 
5. The entire specimen of Spirifer cuspidatus from Millecent, 
figured by him in his ‘Carboniferous Brachiopoda’ (plate 8. 
fig. 19) as a typical representative of the species. The shell of 
this specimen is so well preserved that lamelle scaled off from 
it could scarcely be distinguished from those of a recent Rhyn- 
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 lamelle 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 1-300th of an 
* A fully illustrated description of this genus, by Mr. Davidson, will be 
found in the ensuing (July) Number of the Geological Magazine. 
