202 PALEONTOLOGY OF OHIO. 



arrangement. In parts of the corailum the calices are regularly hex- 

 agonal, but over the greater portion of the surface they are obliquely 

 rhombic, and are arranged in regular diagonal lines, the direction of 

 which, however, changes repeatedly within short distances, giving to the 

 corailum a most peculiar appearance. In any portion of the corailum in 

 which this arrangement obtains, the calices are arranged in a double 

 series of curved or nearly straight diagonals, the one set crossing the 

 branch transversely, whilst the other series is nearly vertical and corre- 

 sponds more or less with the axis of the stem. The corallites are nearly 

 equal in size, and there are no verj'' minute tubuli interspersed amongst 

 the average ones. Occasionally a few corallites occur which are slightly 

 larger than the average, but the surface exhibits no tubercles nor any 

 regular groups of large sized corallites. 



This species is related somewhat to Chsetetes {Monticulipora) BoiverbanJci, 

 Edw. and Haime, but it differs in its simply ramose mode o^ growth, 

 especially when young, and especially in the much smaller size of the 

 corallites, which are only about half as large. 



Locality and position : Upper part of the Cincinnati group, Ohio. Collected by 

 Mr. U. P. James. 



Chetetes briareus, Nicholson. 



' Plate 21, figs. 13, 13?). 

 Corailum free (?), commencing in a pointed base which does not show 

 any indication of having been at any time attached to any foreign body. 

 Above the base the corailum expands so as to form an inverted and 

 somewh9,t compressed cone. From the top of this cone proceed in one 

 specimen four cylindrical branches, which almost immediately divide 

 each into two branches, thus giving rise to eight vertical, slender stems, 

 which have a diameter of two lines each. The further course and final 

 termination of these branches is not shown, as the specimen is unfor- 

 tunately broken at this point. In another specimen the basal cone gives 

 off only two branches from its summit. These bifurcate, and the branches 

 thus produced bifurcate again, two of the tertiary branches inosculating 

 directly above the basal cone. In this specimen, also, the branches are 

 all broken just above their origin, and their terminations thus remain 

 unknown. Surface smooth, destitute of tubercles, but shoMdng here and 

 there small and irregular groups of corallites, which are very slightly 

 larger than the average. Corallites thick-walled, about eight or ten in 

 the. space of one line, entirely without intermediate minute tubuli. 

 Calices oval or circular. 



