GENERA OF FA VOSITIDJS. 183 



composed of polygonal and closely -contiguous corallites, the 

 walls of which are not only in contact, but are undistinguish- 

 ably amalgamated with one another (PI. IX., figs. 3-3 c). 

 The corallites radiate from the base of attachment, the lower 

 surface being probably covered with an epitheca, and the 

 calices opening upon the convex upper surface (PI. IX., 

 fig. 3). The calices are polygonal, with moderately thick 

 margins, which are crenulated by the rudimentary septa (PI. 

 IX., fig. 3 c). Transverse sections (PI. IX., fig. 3 a) show 

 that the walls of contiguous corallites are completely fused 

 with one another, no trace whatever of the original line of 

 demarcation between neisfhbourinof tubes beinsf recoofnisable 

 under the microscope. Sections of this kind also show the 

 short marginal septa, to the number of from eight to twelve 

 or more in each tube ; while occasionally a mural pore is 

 laid open, connecting the cavities of contiguous corallites 

 directly with one another. Vertical sections (PI. IX., fig. 

 3 b) show that there are numerous thin, horizontal, and 

 complete tabulae ; and in parts where the section more 

 or less nearly coincides with the plane of the walls of any 

 of the tubes, we observe numerous unmistakable mural 

 pores. These apertures differ in no respect from the mural 

 pores of Favosites^ except that they are perhaps proportion- 

 ately smaller, and do not seem to obey any regular law of 

 distribution. 



So far as known, this genus is confined to the Trenton Lime- 

 stone in North America, and it afibrds a very interesting link 

 between the Favositid(^ and the ColiLmnariadcs. It differs 

 from Favosites in the lamellar condition of the septa, which, 

 though rudimentary, are never spiniform ; and in the more 

 minute size and apparently irregular distribution of the mural 

 pores. On the other hand, though agreeing with Columnaria, 

 Goldf., in its general structure and appearance, and especially 

 in the character of its septal apparatus, it is fundamentally 

 distinguished from the latter (as our present knowledge stands) 

 by the perforated condition of its walls. 



