118 BRITISH STROMATOPOROIDS. 



Nich., to be associated with " Caunopora-tubes." On the other hand, there aro 

 various species of the genus Stromatopora which, so far as our present knowledge 

 goes, never give rise to " Caunopora " colonies. Thus, I have never seen any 

 examples of" Caunopora" colonies in the case of the Silurian Stromatoporce, such 

 as S. ti/ptca, 1 Rosen, S. Carteri, n. sp., and S. discoidea, Lonsd., though the first 

 of these is the commonest of all the Silurian Stromatoporoids in this country. So 

 far as I know, indeed, the Silurian Rocks of Britain have as yet yielded no 

 " Gaunoporce." It has, however, been pointed ont by Professor Ferdinand Roemer 

 (' Geol. Mag.,' 1880, p. 345) that the Silurian pebbles of the Drift of Holland and 

 North Germany sometimes yield specimens of" Caunoporce." Of this nature is the 

 fossil described by Goldfuss (' Petref. Germ.,' vol. i, p. 113, Taf. 38, fig. 13) as 

 Syringopora filiformis and subsequently described by Roemer himself as Ueliolites 

 interstincta (' Diluvial Geschiebe von Sadewitz,' p. 24, Taf. 4, fig. 2 c). I have also 

 recently collected in the Silurian Rocks (Upper Oesel Group) of Oesel a number of 

 remarkable specimens of " Caunoporce." These present, however, certain special 

 peculiarities of their own, one of the most important of these being that the 

 enveloping Stromatoporoids appear to be related to the genus Clathrodictyon, the 

 associated species of Stromatopora being seemingly free from " Caunopora-tubes." 

 Upon the whole, considering that the embedded tubes constitute the essential 

 feature upon which Caunopora, Phill., and Diapora, Barg., were founded, the facts 

 above recounted would seem to render it absolutely certain that these names 

 cannot be retained as names of genera. To retain these names would lead us into 

 the position of having a series of forms of Stromatopora and Stromatoporella which 

 could only be separated from a parallel series of forms of Caunopora and Diapora 

 by the fact that the latter possessed embedded tubes, the structure of these tubes 

 being in ah these species essentially the same. As this position appears to me to 

 be a quite untenable one, I shall abandon Caunopora, Phill., and Diapora, Barg., as 

 genera of the Stromatoporoids ; since the attempt to reconstruct these genera by the 

 omission of the " tubes " from the list of their distinctive characters could only 

 lead to confusion. 



1 I Lave recently collected in the Silurian Limestones of Hoheneichen, in Oesel, a remarkable 

 specimen of Stromatopora ttjpjica, Rosen, which has the general aspect of a " Caunopora," with 

 unusually large tubes. In this specimen, however, the embedded tubes differ entirely in their 

 structure from those of all the ordinary " Gaunoporw." Not only do they unquestionably belong to 

 an organism foreign to the Stromatoporoid in which they are enveloped, but they belong to a very 

 peculiar type of Rugose Corals with which I am not otherwise acquainted. 



