Palctozoic Corals of the State of Ohio. 87 



unless some distinction utlier than the mode of growth can be 

 shown to separate tliese two groups. 



Cha'tetes sit/iUarioideSy Nicholson, oji. rit. p. 203, pi. 22. 

 figs. 9, 9 a. 



I have at present only examined longitudinal sections of 

 this species, which, however, are highly characteristic. In 

 the central portion of the coralluni (Pi. V. ^p;. 2), the coral- 

 lites are nearly vertical, with slightly Hexuous walls, and wholly 

 destitute of tabula?. As they ascend from the centre towards 

 the surface the corallites become curved outwards, and a few 

 remote tabula? become developed in them, though these struc- 

 tures are always scanty and may be entirely absent. Between 

 the proper corallites, in the outer portion of their course, are 

 developed minute interstitial tubuli, which are furnished with 

 close-set and regular tabuUe. The plate which 1 have de- 

 scribed as filling up so many of the calices in this form, and 

 which may probably be regarded as a species of operculum, is 

 not visible in sections. 



Chcetetes nodulosus^ Nicholson, ojJ. cit. p. 200, pi. 21. 

 figs. 10, 10 a. 



The longitudinal sections of this species (PI. V. fig. 3) agree 

 with those of the preceding species in many points. The 

 corallites, however, in the ascending portion of their course 

 are furnished with remote but regular tabulae throughout, as 

 they are near the surface also ; the interstitial tubuli which 

 are present, though closely tabulate as in C. sifjillarioiJes, are 

 much less regular and frequent than in the latter species ; and 

 the outline of the surface is broken by projecting "monticules." 

 The external characters of these two species are still more 

 decisively different. 



Chcetetes rugosus, Edwards & Haime. 



Cha-tetes rugosm, Nich. op. cit. p. 193, pi. 21. fig. 2. 



Longitudinal sections of this species, as of the preceding, 

 show that the corallites in the central portion of the corallum 

 are nearly vertical, and that they gradually curve outwards in 

 approaching the surface (PI. \. fig. 4). Some of the coral- 

 lites are of considerable size, and appear to be free from tabulas ; 

 others, rather smaller as a rule, are jirovided with regular 

 transverse tabuhv ; and, lastly, there are a number of minute 

 interstitial tubuli, in which the tabulie are very numerous and 

 closely set. 



7* 



