254 Prof. H. A. Nicholson — On a New Tabulate Coral. 



corallite. Between each pair of septa is a row of large oval or 

 circular mural pores, so that there are from twenty to twenty-four 

 rows of these openings in each corallite, generally about four on each 

 face. Not only are the rows of pores thus extraordinarily numerous, 

 but the pores are of unusually large size, and are placed close 

 together, about three of them occupying the space of one line 

 measured either vertically or transversely. The walls of the corallites 

 thus assume a completely cribriform appearance, and look as if com- 

 posed of a series of vertical pillars (the septa) united by horizontal 

 cross-bars. Tabulfe, in the specimens observed, imperfect, from 

 three to four in one line. 



Fig. 1 . — a. A few of the calices of Columnopora cribriformis, Nicli., viewed from above, 

 of the natural size. 5. Two of the calices enlarged, c. Interior of a corallite 

 greatly magnified, showing the rows of pores between each pair of septa. 



At first sight, especially when viewed from above, Columnopora 

 cribriformis presents a striking resemblance to Columnaria alveolata, 

 Goldfuss ; the shape and size of the corallites being alike in both 

 species. The specimens of Columnaria alveolata which are found in 

 the Trenton Limestone, so far as I have seen, have, also, short septa, 

 in the form of strong ridges, which extend inwards for a very small 

 distance ; and this still further increases the resemblance just spoken 

 of. In the latter species, however, the walls of the corallites are 

 compact, and are not perforated by any pores, and this of itself is a 

 sufficient point of distinction. On the other hand, Columnopora crib- 

 riformis is distinguished from all the massive species of Favosites, 

 both by the well-marked septa and by the large size and enormous 

 number of the mural pores. From MicJielinia, C. cribriformis is 

 separated by the fact that the tabulae are certainly not vesicular, 

 whilst the pores are much larger and more closely set than in any 

 species of the former genus, and the septal system is at the same 

 time much better developed. In the only specimens I have seen, the 

 tabulse of C. cribriformis are poorly preserved, and nothing is left of 

 them except their bases. This state of things, however, is quite 

 commonly observable in specimens of Columnaria and Favosites; and 

 I entertain no doubt but that the tabula of the present form were 

 really complete and in all respects well developed. 



Locality and Formation. — In the Hudson Eiver Group, Eiver Credit, 

 Ontario (collected by Mr. G. J. Hinde). In the Cincinnati Group 

 (Hudson Eiver Formation), near Cincinnati, Ohio (collected by Mr. 

 U. P. James). 



