232 PALEONTOLOGY OF OHIO. 



Of the two specimens examined, one had a diameter of nearly an inch 

 and a half, and the other of ten lines. Both were imbedded in the rock in 

 such a manner as to expose nothing but the flat, discoid, lower surface. 



In many respects this form reminds one oi,Pleurodictyum problematicum, 

 Goldfuss ; but as the affinities of the latter are not altogether certain, and 

 as our specimens undoubtedly belong to Favosites, I have thought it best 

 to consider them as distinct. Even if it were accepted as quite certain 

 that Pleurodictyum problematicum is founded upon casts of a species of 

 Favosites, I should still be disposed to consider the present form as dis- 

 tinct, since its epitheca differs markedly from that of the former in ex- 

 hibiting grooves which indicate in the plainest manner the limits of the 

 superjacent corallites. From the recorded species of Favosites, F. pleuro- 

 dictyoides is sufficiently distinguished by its peculiar form and mode of 

 growth. The walls of the corallites are usually well preserved, and are 

 not amalgamated with one another, whilst they support two rows of 

 alternating mural pores. 



Positwn and locality : Corniferous limestone, Kelley's Island, Ohio. From the col- 

 lection of Prof. Edward Orton. 



Favosites invaginata, Mcholson. 



Plate 23, figs. 7, 7a. 

 Corallum massive, conical, or inversely turbinate, composed of a num- 

 ber of funnel-shaped layers invaginated one within the other, or rather 

 of a number of conical layers which are successively superimposed one 

 upon the other. Apex of the mass obtusely pointed, base deeply con- 

 cave. Corallites short, radiating in each successive layer in all direc- 

 tions from the imaginary center of the colony, polygonal or sub-cylindri- 

 cal in shape, mostly sub-equal, from one-half to two-thirds of a line in 

 diameter, rarely one line. Septa very distinct, extending nearly to the 

 center of the visceral chamber. Tabulae very closely set, and apparently 

 usually incomplete. Mural pores large, round, surrounded by an ele- 

 vated border, in two rows on each face of the corallites, those of each 

 row separated from those of the other by an elevated longitudinal line, 

 and either alternating or opposite to one another. 



I have only seen one large specimen of this singular species, which, 

 though imperfect, has a length of four and a half inches, and a diameter 

 of about four inches at its broader end. The specimen is completely 

 silicified, and its state of preservation is such as to prevent the deter- 

 mination of several points of interest. The entire mass is conical, and 

 is composed of successive layers of corallites, which usually have a thick- 



