77 



CHAPTER IV. 



GENERA OF FAVOSITID/E (coiltimmf). 



Gemis Pachypora, LIndstrom, 1873. 

 (Ofversigt af K. Vetensk. Akad. Forhandl.) 



Gen. Char. — Corallum dendroid or frondescent, of polygonal 

 or subcylindrical corallites, the walls of which are greatly 

 thickened towards their mouths by the deposition of concentric 

 layers of sclerenchyma. Calices sometimes annular, some- 

 times oblique and semi-lunar. Septa in the form of minute 

 spiniform projections, or obsolete. Tabulae complete, remote. 

 Mural pores few in number, irregular, often of large size. 



This genus was founded by Lindstrom for the reception of 

 the single species Pachypora laviellicornis, Lindst., from the 

 Upper Silurian deposits of Gotland, which will be shortly 

 described immediately. So far as mj' investigations have 

 gone, the genus will be found to include a considerable number 

 of types, some of which have been referred to Favosites, while 

 others have been placed in Alveolites. Thus it has been 

 already pointed out by Mr R. Etheridge, jun., and myself 

 (Journ. Linn. Soc, vol. xiii. p. 362), that the so-called Alveo- 

 lites Fisclieri, Bill, and Alveolites frondosa, Nich., of the 

 Devonian deposits of North America, are really referable 

 to Pacliypora ; and I have now determined that the well- 

 known Favosites cristata, E. and H., of the Upper Silurian, 

 and F. cervicornis, De Blainv., of the Devonian, must be 

 placed in the same genus. It is probable, in fact, that all the 



