PAL.E0NTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 493 



extremity are broader and flatter. The first series of primary radials 

 are prominent, and raise out of the basal pit, which they do not in Oli- 

 vanites Verneuilii. Viewed from either end, this species presents an 

 irregularly sided pentagon, the bounding lines of which are concave 

 toward the body of the specimen. This striking difference of section 

 transversely, will at once distinguish this from 0. Verneuilii. 



Geological position and locality. — A few specimens of this species 

 have been found Jn the rocks of the Denovian period, lying between 

 the black slate and the hydraulic cement beds at Rock Island, at the 

 foot of the Falls of the Ohio ; on Beargrass creek, near Louisville ; 

 also, on Silver creek, Clarke county, Indiana. They have a limited 

 vertical range, and are only found near the base of the beds in which 

 they occur. Olivanites Verneuilii does not, so far as our observation ex- 

 tends, rise into the beds above the hydraulic beds, in which it is 

 not found. 



COD ASTER ALTERNATUS. Eyon. 

 (Plate 3, 3 o, 3 6.) 



Body long ; irregularly conical ; summit level in the centre ; slop- 

 ing, slightly toward the outer end of the pseudambulacral fields ; hor- 

 izontal section at the lower extremity of the fields pentagonal, the 

 angles of the pentagon being at the ends of the pseudambulacral field. 



Basal pieces three ; pentagonal ; of equal size ; gibbous ; when 

 joined forming a minute triangular cup, larger than the inferior extrem- 

 ity of the joined first radials fitting upon it ; perforated in the centre 

 by a very small circular opening. 



Radial pieces ; three — two hexagonal complete, one pentagonal, and 

 incomplete, (as in penlremites); the upper margin of the hexagonal 

 pieces are concave in the centre, the corners obliquely truncated, form- 

 ing, with the pentagonal piece, a deep cup, having the upper margin 

 indented with two concave and three angular notches, from which rise 

 five radials of the second series, two fitting upon the concave notches 

 at the summits of the complete pieces ; the other three rising from the 

 angular notches between the three pieces. 



Radial pieces, second series, five ; reaching the summit ; twice as 

 long as wide ; the summit of each indented by an angular notch, 

 broader than deep ; rising from the base of each, and tapering to a 

 poinkat the inferior extremities of the notches, is an elevated rounded 



