54 



THE GEOLOGIST. 



author's C. globulina, the matter may perhaps demand some further 

 examination. 



Strophomena analog a. — 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. rliomboi- 

 dalis (Silurian) and the St. analog a ; 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. 



Streptorhyncus 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 further 

 examination and study, so as to determine whether they should be 

 considered more than varieties of S. crenistria ? I have therefore pro- 

 visionally retained the following designations, S. arachnoidea, S. Kelln, 

 S. cylindrica, 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. Darwinianci) 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 Orthis? 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. 



ProductuL— 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 monograph 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. 



Productus gigcmteus is both the largest and typical species of the 

 genus, but very variable in its shape. Large examples are abundant 

 in ecu-tain localities; while young specimens appear to be less com- 

 monly found or collected. 



V. hemisphcericios is a badly made out species ? and I am not jet 

 able to concur 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, 



