190 PALEONTOLOGY OF OHIO. 



cylindrical, radiated frora a center or an imaginary axis, contracted at 

 irregular distances, but in planes parallel to the surface of the specimen ; 

 tubular mouths closed at final period of growth; ridges bounding the 

 mouths, granulated or tuberculated ; additional, tubes interpolated." 

 (Physical Description of New South Wales, Stryzelecki, p. 262, 1845.) I 

 have already pointed out that the mode of- growth is a character which 

 can only occasionally be recognized in practice, and, at any rate, in this 

 character Stenopora does not differ from Monticulipora. Leaving this out 

 of the question, therefore, the distinctive characters of StenojMra are to 

 be found in the granulated, tuberculated, or spinose mouths of the coral- 

 lites, the final closure of the calices, and the constrictions of the coral- 

 lites in planes parallel to the surface. Two or three species of Clisetetes, 

 from the Palaeozoic deposits of North America, exhibits tuberculated or 

 sj)inose margins to the calices, but none of them exhibit the other char- 

 acters of Stenopora, and I have, therefore, come to the conclusion that 

 none of our forms can be referred to this genus. 



For the reasons above given, then, I shall consider all the corals here 

 referred to as belonging to the genus Cheetetes, irrespective of the fact that 

 many of them have been formerly placed by eminent palaeontologists 

 under the genus Monticulipora, and others of them have been put under 

 Stenopora. The Lower Silurian deposits of .Ohio have jaelded a magnifi- 

 cent series of corals of this nature — a series which is remarkable not 

 only for the wide range of specific variation which it exhibits, but also 

 for the vast abundance of individuals belonging to the commoner species, 

 and the great beauty and perfection of their preservation in very many 

 instances. From their small size, the characters which separate many 

 of the species are necessarily minute and difficult of detection, except by 

 the exercise of considerable care, and by the comparison of a number of 

 specimens with one another. Some of the species hereafter described 

 are very nearly allied to one another, and iri other instances individual 

 specimens may be found which seem to stand midway between two 

 species, and can not readily or definitely be referred to either. This 

 would give countenance to the belief that future researches might ulti- 

 mately enable us to unite some of these so-called species under one or 

 more highly variable specific types. Nevertheless, it seems clearly 

 necessary, on behalf of the working palaeontologist, _ to give separate 

 titles to these nearly allied forms, and the drawbacks which notoriously 

 attend the placing of many varieties under a single species render it 

 advisable, in practice, to make these titles of specific value. 



The diflTerent species of Chsetefes, in the wide sense here understood, 

 may be conveniently, if not altogether in accordance with nature, 



