112 BRITISH STROMATOPOROIDS. 



preserved. It is therefore extremely probable that the tubes of many of the 

 " Caunoporm " and " Diaporce " are really destitute of anything of the nature of 

 septa. On the other hand, I have recently found a number of " Gaunoporce " in 

 the Devonian Rocks of the Eifel, in which the " tubes " are furnished with well- 

 preserved and quite unmistakeable septal spines. In such cases the septal spines 

 are arranged in vertical rows in the interior of the tubes, eight of such rows beino- 

 apparently the general number. The spines are altogether of the type of these struc- 

 tures, as seen in many species of Favosites or in Syringopora. They have the form 

 of blunt calcareous spines (Fig. 17), which fall short of the centre of the tubes, and 



Fig. 17. 



Fig. 17. — Sections of a species of Stromatopora, from the Devonian Limestone of Gerolstein, 

 enlarged twelve times, showing " Caunopora-tubes " with septal spines. A. Tangential 

 section. B. Vertical section 



are often quite marginal. They are most easily recognised, as a rule, in longitu- 

 dinal sections, in which they are transversely divided near their bases, and appear 

 in the interior of the tubes as rows of dark round spots (Fig. 17, b). I may add 

 that in a specimen of " Caunopora " from the Corniferous Limestone of Ontario > 

 which Dr. Hinde was so good as to submit to me, I have found similar but even 

 more largely developed septal spines. 



Another point in which great variations exist among the so-called " Gaunoporce " 

 is as to the mode of growth of the tubes. In some specimens, which, however, are 

 by no means typical ones, the " Caunopora-tubes " are very irregular in their 

 growth, being often far apart, and not extending their vertical growth to any great 

 distance from the horizontal stolons to which they are attached. In such speci- 

 mens, the " Caunopora-tubes," if divested of the enveloping Stromatoporoid, might 

 fairly enough represent an ordinary Aulopora colony, in which the tubes had grown 

 to a much greater height than is usual in the genus Aulopora, and had also become 

 here and there connected by an occasional cross-tube. This is the condition of 

 things, for example, in the specimen from the Corniferous Limestone just alluded 

 to. In the great majority of the " Gaunoporce," however, the tubes are placed close 

 together, and usually at tolerably regular intervals, and they grow straight upwards 

 for very considerable distances. Owing to the fact that it is not possible to make 



