NATURAL SCIENCES OF PHILADELPHIA. 413 



is large, hexagonal resting in the angular notch between the first radials, it 

 supports two pieces of the second series, these again three pieces. All the pieces 

 from the base to the summit of the second radials are well defined by a deep 

 groove at the base of their junction with each other ; above this the pieces 

 rise upon a surface quite smooth, and are more readily distinguished by the 

 spine marking the centre of each piece, than by the line of their union with 

 each other. The first anal piece is like the first radial pieces, it supports one 

 hexagonal piece on its centre, and a pentagonal piece on each of its oblique 

 upper sides ; this group of four pieces are nearly of the same size and are 

 slightly convex ; they support about six rows of pieces one above the other, 

 each row diminishing in size and number of each row, in all about twenty- 

 five pieces, each piece having a central spine or tubercle. The summit is low, 

 deeply depressed between the groups of arms, surmounted by a subcentral 

 proboscis, covered by numerous polygonal pieces nearly of the same size, 

 separated by well defined grooves. The arms appear to be ten in number, the 

 postero-lateral rays are not seen ; it is possible they may bear three each ; 

 should this be the case, the whole number of arms would be twelve. The arm 

 facets are large and prominent ; a small portion of one of the arms remaining 

 on the specimen, shows them to be composed of a double row of thin pieces. 



Dimensions. 



Height to free arms '48-100 inch. 



Height to base of proboscis '85-100 " 



Diameter below arms "95-100 " 



Geological positivn and locality. Collected by Dr. J. Knapp, from the 

 urinoid bed immediately below the hydraulic limestone, Clark county, Indi- 

 ana. 



I take pleasure in dedicating this species to a cultivator of Geology, my 

 friend, Dr. J. Knapp of Louisville, Ky. 



Magestocrinus spinosulus, n. s. Plate iv., fig. 7 a-b. 

 Body subcylindrical, expanding slightly from the middle of the third pri- 

 mary radial to the summit of the third secondary radials. The first three or 

 four axillary pieces lying nearly horizontal, expand the body at the inser- 

 tion of the arms. The base is nearly level to the end of the spines on the 

 third primary radial, concave from the middle of the second radial to the cen- 

 tre of the basal pieces ; the summit is low, arched, surmounted by a proboscis 

 placed quite near the side of the summit above the anal side. Basal pieces : 

 together they form nearly a circle, slightly indented at the sutures at which 

 they are united, crenulated on the outer margin of the columnar facet, form- 

 ing a thin disk, implanted upon the second circle of pieces, a little larger when 

 joined to the body than at the union with the column. The pieces appear to 

 be joined to the second circle by lapping, and not at the edges of the pieces. 

 First primary radials five, hexagonal, nearly equal in size, differing slightly 

 in form, summits nearly parallel to the base of the pieces, curving outward 

 and downward at the outer extremity of each. Second primary radials hex- 

 agonal, the centre of each having a mammillary tubercle more or less prominent. 

 Third radials larger than the second, pentagonal, differing considerably in 

 size and form ; the centre of each piece is surmounted by a short mammillary or 

 spinous tubercle, the base of which covers -nearly or the entire surface of the 

 pieces, on the upper oblique margins of each rests two hexagonal or septag- 

 onal pieces ; each of which bears like the third radials a spine or tubercle, 

 which are rather smaller than those on the radial below them, on which they 

 rest. These last pieces are also axillary, and support each two smaller pieces 

 more or less spinous, the last two pieces nearest each other (or in the centre 

 of the several rays,) are also axillary and support each two small pieces, one 

 above the other, the outer pieces supporting three similar pieces, all of which 



1861] 



