OF DENISON UNIVERSITY. 12 1 



rugae which striate the surface are more or less radial at the mouth of 

 the pits but as they descend the elevation they rapidly take a common 

 direction and become quite parallel and more or less wavy between 

 the elevations. The direction of the striae then is transverse to the 

 direction in which the elevations are said to be more readily referable 

 to series. This arrangement is very common in the genus Smif/iia of 

 Edwards and Haine, a subgenus of Phillipsastrcea, D'Drbigny. 



The specimen referred to this species by Mr. William J. Davis. 

 (Kentucky Fossil Corals, PI. 123, Fig. i,) has not the slightest resem 

 blance either to the type or to the Onio specimen here under consid- 

 eration ; it belongs rather to that smaller variety of 5 pentagonus which 

 is usually regarded as typical of the species. 6". incertus, Davis of the 

 same plate is a good medium sized specimen of the same species. 

 5. pciita^:^oniis, Fig. 3, of PI. 12:, is a similar f>rm with a slightly less 

 distinct margin around the pits in the centre of the calyces. S. s!n- 

 atus. Fig. I, of PI. 122. represents one of the larger varieties, k formi 

 slightly less in size, with more defined margins about the pits, is fig- 

 ured by Rominger, Fossil Corals, PI. 48, Fig. \. His fii^ure 2 of the 

 same plate represents one of the smaller forms. The species is e.x- 

 tremely variable both in the size of the calyces, and in the fineness of 

 their radial striations. Variation is however the normal condition of 

 species of wide geographical distribution. 



Sph.erexochus mirus. Bey rich. 

 {Plate XIII, 7v> 6.) 



Since Hall, in the Geol. Rep. of Wisconsin. 1862, separated Sph. 

 Romingeri from Sph. mirus, on account of distinctions presented b\ 

 the pygidia at that time associated with undoubted glabellne of a spe- 

 cies of Sphcerexochus, it has been the fashion of American paleontolo- 

 gists to refer all American specimens to Hall's species. To show that 

 this is probably incorrect, a description of the glabella of a specimen 

 obtained in the Guelph at Cedarville, Ohio, is appended, which will 

 be seen to agree even in the minutest details with the European forms, 

 referred to Beyrich's species. 



Glabella almost hemispherical, slightly broader than long; two- 

 small lobes cut off a part of each side of the glabella at the occipital 



