94 BRITISH STROMATOPOROIDS. 



tions are simply transverse, but in other cases they may be vesicular, or almost 

 funnel-shaped. Very probably connected with these astrorhizal tabulae are the 

 curved, oblique, or irregular partitions which are seen crossing the interlaminar 

 spaces in almost all the species of Stromatoporella (Plate VII, fig. 4). 



Many of the types which exhibit the above general characters are encrusting, 

 but they are by no means always so, and 8. granulata, Nich., the type- species, 

 appears to be always a free laminar expansion, with a basal epitheca. Not only 

 are they very variable as to their mode of growth and general form, but they also 

 vary much as to certain details in their actual structure. 



Much more labour, therefore, will be required before it will be possible to 

 speak positively as to the number and limits of the species which belong here. 

 All the forms of this genus which have come under my observation belong to the 

 Devonian formation. The type-species is 8. granulata, Nich. (' Ann. and Mag. 

 Nat. Hist.,' 1873), which is abundant in the Hamilton and Corniferous formations 

 of Western Canada. Closely allied to this is a beautiful species which occurs 

 commonly in the Devonian Limestones of the Bifel, and which I shall provisionally 

 name 8. eifeliensis. The microscopic structure of these two forms (Plate VII, 

 figs. 3 and 4, and figs. 5 and 6) is very much the same ; but 8. eifeliensis possesses 

 remarkably well-developed astrorhizas, and has certain other structural peculiarities 

 which will probably entitle it to specific distinction. In various features, the form 

 described by Mr. Carter as Stromatopora dartingtonensis makes a close approach 

 to the above-mentioned forms ; but it seems to possess some special characters of 

 its own, and will require further investigation. Related to the preceding also 

 is the singular Stromatoporoid of the Devonian Limestones of the Paffrath district, 

 which Bargatzky described as Diapora laminata, and on which he founded the 

 genus Diapora. This being the case, it might have been proper, in accordance 

 with the strict laws of priority, to retain the name of Diapora for the present 

 genus. Bargatzky, however, made the essential character of his genus Diapora 

 to consist in the possession of thick- walled " Caunopora" tubes, the genus being 

 only separated from the so-called " Caunopora " of Phillips by the character of the 

 tissue surrounding these tubes. As, however, I am able to show that the said 

 thick-walled tubes — whatever their nature may be — are merely of occasional 

 occurrence, and that they only constitute a particular phase in the history of 

 certain kinds of Stromatoporoids, it seems clear that it would be highly unadvisable 

 to retain the names Caunopora, Phill., and Diapora, Barg., as the titles of generic 

 divisions. It could, in fact, only lead to confusion to retain these names for forms 

 in which the characteristic thick-walled tubes, upon the existence of which these 

 genera were established, are commonly wholly wanting. For this reason, there- 

 fore, I have thought it best to give the new name of Stromatoporella to the group 

 of forms at present in question. 



