128 Reviews — Prof. Dr. Nicholson — British Stromatoporoids. 



that whilst it may seem reasonable to suppose that the former were 

 occupied by a stolon or axis of the coenosarc, the same explanation 

 will hardly suffice for the latter, in which the axial canal is some- 

 times 10 mm. in diameter. On the whole, whilst fully appreciating 

 the significance of the facts brought forward by Prof. Nicholson, we 

 should feel disposed to wait for further evidence before definitely 

 accepting Beatricea as a genus of Stromatoporoids. 



(VI.) The Nature of Caunopora. — The author discusses in detail the 

 much-debated subject of the nature of the Stromatoporoids, in which 

 the coenosteum is traversed by thick-walled tubes at right angles to 

 the concentric lamina? of the fossil. These tubes are frequently 

 tabulate, and in some cases they possess spines resembling the spinal 

 septa of Favosites or Syringopora, and they are usually all connected 

 together and open into each other, whilst at the same time no com- 

 munication can be traced between them and the interlaminar spaces 

 of the Stromatopora itself. Prof. Nicholson has established the fact 

 that in several distinct species of Stromatopora and Strom atoporella, 

 there are two states of the same species occurring in the same locality, 

 one, in which the so-called " Caimopora " tubes are present, and the 

 other in which these structures are entirely wanting. It follows from 

 this, that the existence of these tubes can in no wise characterize a 

 particular genus, and therefore the names of Caunopora, Phill., and 

 Diapora, Barg., must be abandoned. 



In character these " Caunopora " tubes closely resemble the tubes 

 of Syringopora and Aulopora, and by Eoemer, Carter, and others 

 they are believed to be independent organisms enveloped in the 

 growth of the Stromatopora. There are certain difficulties against 

 the acceptance of this theory ; one is the fact, that many of these 

 tubes are not known independent of their Stromatopora envelopment. 

 The " Caunopora " tubes often occur also in localities where indepen- 

 dent forms of Syringopora are altogether absent, and on the other 

 hand, where the corals are abundant, the " Caunopora " forms of 

 Stromatopora are rare. It is possible that, owing to the commensal 

 mode of growth, distinct forms of Syringopora and Aulopora may 

 have been produced. The author arrives at the conclusion that 

 "the fossils ordinarily called ' Caunoporce' and ' Diapora}' are the 

 result of the combined growth of some Stromatoporoid with some 

 Coral, the former usually being a species of Stromatopora or Stroma- 

 toporella, and the latter generally belonging either to Syringopora or 

 to Aulopora." 



In concluding this notice, we may call attention to the beautiful 

 plates in which the minute structures of the organisms described are 

 fully illustrated. The plates have been drawn by the author and 

 lithographed by Mr. Hollick. This first part of the Monograph 

 needs no commendation. It is a very important contribution to the 

 knowledge of a most puzzling group of organisms, and the subject is 

 treated with that thoroughness which specially characterizes Prof. 

 Nicholson's work. Gr. J. H. 



