COEALS OF THE CINCINNATI GEOUP. 189 



peculiarity is stated to be recognizable in practice by the fact that a 

 rough fracture of the coral exposes the interior of the tubes, instead of 

 bringing the exterior of the corallites into view, and it is remarkably 

 well shown in the figures of C radians, given by Lonsdale. (Geology of 

 Russia in Europe, Appendix, pi. A, fig. 9a.) Subsequent palaeontologists 

 have for the most part accepted this distinction, and it was chiefly on 

 account of this character that Mr. Lonsdale proposed the genus Steno- 

 pora, and M. D'Orbigny that of Monticulipora, for corals in other respects 

 essentially similar to the type forms of Chsetetes. I have elsewhere dis- 

 cussed this question at greater length, and shall simply remark here that I 

 find it impossible to accept this distinction in the meanwhile as separating 

 the genera Chsetetes and Monticulipora, whilst the genus Stenopora, though 

 very possibly to be retained for the forms originally placed under it, can 

 not with propriety be held to include the corals generally referred to it 

 by European palaeontologists. Apart from other grounds, it appears to 

 me that this course is unavoidable, if only upon the ground that the dis- 

 tinction by which it is sought to separate the genera Chsetetes and Monti- 

 culipora is one which can only very rarely be applied in practice with 

 any certainty. Many corals which would have to be referred to one or 

 other of these genera are so minute as to render the determination of 

 their mode of growth a matter of the utmost difficulty, if not an absolute 

 impossibility, whilst the results yielded by fracture of the coral are by no 

 means invariable, the same species splitting in such a manner as at one 

 time to show the interior of the corallites, and at another time the ex- 

 terior. In illustration of the difficulty which the best observers may 

 find in determining the mode of growth of these corals, it may be men- 

 tioned that the familiar Chsetetes petropolitanus. Pander, is stated by Lons- 

 dale to divide fissiporously, and to be referable to the genus Chsetetes, as 

 restricted by him. On the other hand, the very common coral which 

 American palaeontologists have almost unanimously recognized as being 

 Chsetetes petropolitanus, Pander, increases by gemmation, a rough fracture 

 almost always exhibiting the exterior of the corallitee, so that it would 

 thus have to be placed in either Monticulipora or Stenopora. Hence it 

 would appear that some more satisfactory dfetinction must be pointed 

 out before we can with certainty separate the genera Chsetetes and Monti- 

 culipora, since these are not supposed to differ in any character of im- 

 portance except their mode of growth. 



The genus Stenopora, Lonsdale, has not uncommonly been quoted by 

 American palasontologists, but I have seen no specimens which could 

 properly be referred to it. It is defined by Mr. Lonsdale as follows : " A 

 ramose, spherical, or amorphous, tubular polypidom ; tubes polygonal or 



