396 J. Hall on Cryptonella, Centroneila, Meristella, 
raising a cohering disc from its surface. There was no ¢ 
point between the disc and the disc-reflection, but a seemingly 
distinct curve, concave outwards. As the dise rose above the 
water, this curve opened, and a broad connecting column 
to bind the dise and its reflection, just like a coherent water 
column between the lifted — and the level water surface. In- 
material connection between the disc and reflection was perfect, 
both before and at the instant of visible separation, This ob- 
servation has interest in its relation to the contact a of 
eclipses. 
Art. XLI.— Observations upon some of the Brachiopoda, with réf- 
erence to the genera i gens ec bopae Meristella, and allied 
; by L. ract of a paper read before the 
Albany Institute, Heute 3, 1863. (Communicated by 
_ the author.) 
“IN the sa a the Paleozoic Brachiopoda, we 
the general external form, and ine of + 
the shell, for detetmiontion of the generic relations, until more 
extensive collections may furnish us with weathered specimens, 
or with crystalline or silicified ones, which, admitting of being i 
cut, and macerated in acid, will enable us to ascertain the true 
interior characters. 
In many instances, so nearly do very distinct genera approac 
each other in their external form, that reliance on this alone i 
very uncertain, and will surely lead to much confusion, if insis 
upon as the means of generic se tetan ores of 
For a long time, and vie e began to it mene 
belong to distinct nies were embraced in che ‘esate ' 
Terebratula and Atrypa, At a later period, when the gen 
Rhynchonella had been ean in its application to beg 
seozoic species, we find numerous species, which from @ 
ternal form had been pedorred oe that genus, possessing ¢ 
incompatible with it 
— of the most common of these is Zerebratula ouneata = : 
cuneata = Retzia cuneata, and which will pro 
arena aemh pbeerystions by the 
1 the stenetions of the erraions by the author. rr comin 
