20 PROCEEDINGS OF THE AMERICAN ACADEMY 



each give off two slender fingers, which are composed of the following 

 pieces : first, one or two quadrangular ones, upon them from five to 

 seven somewhat smaller wedge-formed ones placed one above another, 

 the large end of one wedge being placed over the small end of the 

 next, the wedges becoming gradually more acute, until on the sixth or 

 seventh piece there commences a double row of small, quite acute, 

 pentangular pieces, which alternate with each other, the salient edges 

 of one row fitting into the retreating angles of the other row, the 

 points of their junction being lateral, not central, as in most otlier 

 genera having similar arms. Yet two more fingers exist on each 

 arm ; they are situated on the outer surfaces of the six pieces described 

 above (the first one on the second piece from the last radial, the 

 second one on the fourth piece from the same radial), the inner sur- 

 faces having no branches, and lying close together throughout their 

 whole extension. They spring apparently from the sides of the pieces, 

 the facets being on the sides, rather than on the top as in a regular 

 axillary piece ; curving out gracefully for a short distance, they con- 

 tinue in a straight line to their ends without any further bifurcation. 

 They are slender, composed of pieces exactly similar to those of the 

 fingers already described. On either side of the ambulacral grooves 

 of the fingers is a row of stout pinnulae. 



Dimensions : — 



Height of calyx to insertion of arms . . . .55 inch. 



Diameter at the arms ...... .85 " 



Height of basal pieces .26 " 



Length of arms 2.00 « 



Length of proboscis (variable proportion in diff. sp.) .GO " 



Geological Positio7i and Locality. Rare in the silicious mud beds 

 at the top of the Knob member of the subcarboniferous limestone, 

 Hardin County, Kentucky ; Montgomery County, Indiana, «&;c. 



DiCHOCRINUS SYMMETRICUS, Sp. NoV. 



Body. The general form of the body is subconical ; from the basis 

 to the sununit of the first radials it is basin-formed, above which it 

 contracts upward and terminates in a point, formed by the large spinous 

 piece which surmounts the vault. 



The hasal pieces, two in number, are of equal size, pentagonal ; line 

 of junction with each other straight, forming when united an irregu- 



