NATURAL SCIENCES OF PHILADELPHIA. ]29 



prominent, near one-third as wide as the plate, and extending down between 

 one-third and one-half its length. Second radial pieces small, extending out 

 nearly horizontally from the first ; round below, and presenting a pentagonal 

 outline, as seen from the under side, supporting on their superior (outer) 

 sloping sides, the two first divisions of the arms. First anal piece rather large 

 for a species of this genus, apparently pentagonal, and extending down between 

 the first radials, nearly as deep as the articulating facets supporting the second 

 radial pieces. (Other parts unknown.) 



The sutures separating the first radial plates from each other, and from the 

 base, are rather distinctly canaliculated, in consequence of the beveling of the 

 edges of the plates. The surface is finely granulose, and ornamented by small 

 obscurely subnodose costae, of which there are two on the base passing around 

 near the margin. Three similar costae ornament the first radial plates, being 

 arranged parallel to the basal and lateral margins, but becoming nearly or 

 quite obsolete above the middle. 



Named in honor of Prof. Richard Owen, of the Geological Survey of Indiana. 



Locality and position. Burlington, Iowa. Burlington Limestone. Collec- 

 tion of Mr. Charles Wachsmuth. 



Platycrinus scobina. Body rather small, cup-shaped or subturbinate below 

 the summit of the first radial pieces. Base basin-shaped, about twice as wide 

 as high, and rather more than equalling one-third the height of the body to 

 the top of the first radials ; pentahedral in outline, with slightly concave 

 sides, columnar facet less than one-third the breadth of the base. First radial 

 plates slightly broader than high, widening a little upwards from the base, 

 presenting a subangular outline, the superior lateral angles being truncated 

 for the reception of the anal and interradial pieces ; facet for the reception of 

 the second radial piece not protuberant, concave, rather less than one-third the 

 breadth of the upper side of the first radial plates, and extending down about 

 one-fifth their length. Second radial pieces small, triangular, and supporting 

 on their superior sloping sides the first divisions of the arms. After dividing 

 on the second radial pieces, the arms divide again on the second piece above, 

 beyond which they are long, slender, and apparently simple. After the second 

 bifurcation, they are each at first composed of a single series of wedge-shaped 

 pieces, but gradually pass into a double alternating series of pieces, each of 

 which is about as long as wide. 



The surface of the basal and first radial plates is ornamented with numerous 

 small, rather sharply elevated, irregularly arranged nodes, or coarse granules, 

 so as to present a rasp-like appearance. The sutures are closely anchylosed in 

 the base, and well defined between the first radial plates. 



In its surface markings this species is much like P. Wortheni of Hall, but it 

 differs in having a distinctly protuberant, instead of a flat or concave base, 

 and in having but four arms to each ray, instead of eight or nine. 



Locality and position. Burlington, Iowa. Burlington Limestone. Mr. 

 Charles Wachsmuth's collection. 



Platyckinus (Pledeocrinus) asper. Body small, rather deeply basin- 

 shaped below the arms. Base much depressed, largely and deeply excavated 

 below, with a narrow prominent marginal rim, which is notched at the 

 sutures, and somewhat undulated. First radial plates broader than high, 

 widening moderately upwards and presenting a subquadrangular outline, 

 but really hexagonal, in consequence of the truncation of the superior 

 lateral angles for the reception of the interradial and anal plates ; sinus in 

 the summit of each, for the reception of the second radials, deep, semi- 

 circular, and equalling about half the breadth of the upper side ; surface 

 of each ornamented by a very prominent, sharply elevated carina, which 

 passes across near the lower side, and is waved or often broken up into isola- 

 ted prominences. Second radial pieces triangular, wider than long, and 

 1861.] 



