140 Cincinnati Society of Natural History. 



DESCRIPTION- OF FOUR NEW SPECIES OF SILURIAN 



FOSSILS. 



By S. A. Miller, Esq. 



EUCALYPTOCRINUS (HyPANTHOCRINUs) EGANI, D. Sp. 



(Plate IV., fig. 1, cast of the calyx and the dome; fig. 1«, cast of the dome, the canal 

 leading from it, the expansion at the top of the interbraehials and extension above, where 

 it was covered by plates: fig, lb, east of the body, dome and interbraehials; fig. Ic, cast of 

 the canal showing the markings of the plates above the interbraehials, and^the evidences of 

 the attachment of the latter to the dome.) 



The general form of the calyx is ohcoDical, with a truncated base 

 for the columnar attachment. Height and width about equal. With 

 the brachial and interbrachial plates and arms attached, the form is 

 cylindrico-elliptical. The basal plates form a regular pentagon, upon 

 the sides of which the first radials rest. The first radial plates are 

 hexagonal, longer than wide, and larger than the succeeding ones. 

 The second radials are somewhat quadrangular; the greater width is 

 at the base, which is slightly convex, and rests upon the superior con- 

 cave side of the first radials. The third radials are hexagonal, the 

 superior side being the shorter, and the lower lateral sides being- 

 shorter than the other three. The first supr^b- radials are pentagonal 

 and less than half the size of the third radials. The second supra- 

 radials are smaller than the first, pentagonal and support the arm 

 plates. The inter-supra-radials support interbraehials. The inter- 

 radials consist of one large ten-sided plate, having a length more than 

 twice its greatest diameter, and supporting upon its upper face two 

 interradials that support interbraehials. 



It will at once be observed, that this formula of the plates is that of 

 Eiocalyptocrimcs, and that the calyx may be distinguished from E. 

 crassus only b}^ the more elongated form of the body and plates. 



Above the calj^x, however, the species are distinguished b}' more 

 marked and decided characters. 



The cast of the dome, immediatel}' covering t'he cavity of the calyx, 

 has a height above the cal3^x about equal to its diameter. Two little 

 projections, at the top of the calyx, between the interbraehials, remain 

 upon the casts, to show the connection between the arm furrows and 

 the interior of the body. The interbraehials were firmly interlocked 

 with the dome as shown by the widened concave edge and the three 

 slits in each, as well as by the angular and indented surface markings 

 of the dome. The cast of the canal leading from the dome to the top 



