54 
THE GEOLOrxlST. 
author's C. glohuJina, the matter may perhaps demand some further 
examination. 
Stropliomena analoga. — This species appears to have been recurrent 
from the Silurian and Devonian periods ; and although certain small 
differences of secondary value may be observed in the St. rJiomhoi- 
dalis (Silurian) and the St. analoga ; they are both constructed on a 
similar model, and appear to be varieties of a single species. As 
however some small differences in detail may be noticed in the 
Carboniferous shell, the term analoga should perhaps be retained, if 
not as a specific, at least as a varietal designation. 
Streptorkyncus crenistria, Phillips. Many so-termed species have 
been fabricated out of varieties or variations in the shape of this very 
variable shell; and of which the larger number (if not all) are undoubted 
synonyms. Three or four of these may however still demand farther 
examination and study, so as to determine whether they should be 
considered more than varieties of S. crenistna ? I have therefore pro- 
visionally retained the following designations, S. arachnoidea, S. Kellii, 
S. cijlindnca, and S. radialis, as named varieties of S. crenistria. Of S. 
cylindrica I have never seen any other than the type, and although 
S. Kellii is stated to be plentiful in certain Irish localities, but three 
specimens in all have passed under my observation. Prof. Phillips 
informs me that he believes S. radialis to be quite distinguishable 
and distinct (except from S. Barwiniana) from S. crenistria; and M. 
De Verneuil expresses a similar opinion. 
Orthis. — Of this genus 0. resupinata, 0 Michelini, and 0. Keyserlin- 
giana are well made out species; but the Ortliis? antiquata has not 
been sufficiently studied ; and indeed all my efforts have been 
unsuccessful to procure the sight of any other than the original 
specimen figured in the Geology of Yorkshire, now in the British 
Museum. 
Productics. — Of this genus some thirty species have been retained : 
nor does the attentive study I have made of the species lead me to 
imagine them more variable or difficult of recognition or identification 
than are the other Brachiopoda of the Carboniferous period; but 
have been perhaps less attentively studied by the generality of 
geologists. In my monogTaph I have endeavoured to describe and 
illustrate all their external and internal details ; but with reference 
to some few the material in my possession or at command was insuffi- 
cient ; and I would urge upon those who may be favourably located 
to search for specimens which would enable palaeontologists to clear 
away those doubts that may still remain unsolved. 
Froductus giganteus is both the largest and typical species of the 
genus, but very variable in its shape. Large examples are abundant 
in certain localities ; while young specimens appear to be less com- 
monly found or collected. 
P. liemisplirEncus is a badly made out species ? and I am not yet 
able to concui' in the opinion recently expressed upon the subject by 
my learned and much esteemed friend. Prof, de Koninck ; and to 
whose labours science is so much indebted. I am, on the contrary, 
