88 WINCIIELL AND MARCY ON FOSSILS FROM THE 



Body large and massive, somewhat obconic, spreading more rapidly towards the arm 

 bases ; base sub-acute, generally turned to one side. Basal plates three, equal, hexagonal 

 — the inner side very short — a little broader than high. Radials three in each series. Of 

 the first radials three stand opposite the three basals, and are hexagonal, a little higher than 

 wide, the upper side being shortest, the lower next in length. The other two first radials 

 stand opposite the division between two basals; they are heptagonal by the division of the 

 base, the two basal sides, however, lying nearly in the same straight line. The second ra- 

 dials are hexagonal, nearly as large as the first, one fifth longer than wide, the upper and 

 lower sides about half the length of the others. The third radials are larger than the sec- 

 ond, octagonal in the anterior and anterolateral rays, having two upper sides, each of 

 which is about equal to the lower one, the lateral sides being considerably the longest, 

 and thus causing this plate to be longer than broad ; in the postero-lateral rays they are 

 heptagonal by the enlargement of the anal plates. The first supraradial plates are irreg- 

 ularly hej^tagonal, two thirds as large as the third radial. Second supraradials heptagonal or 

 octagonal, of the same size as the first or smaller, supporting on their upper sloping sides a 

 pair of small pentagonal brachials. Number of arms twenty. First regular interradial hexa- 

 gonal, nearly as large as the first radials, supporting on its shorter upper sides a pair of 

 smaller interradials, whicli are succeeded by about ten other interradials, making thirteen 

 in all. The azygos, or anal interradials number about thirty. The first rests upon the 

 basals, and has precisely the same form and size as the antero-lateral first radials ; like the 

 radials, also, it is succeeded by two others, producing a series resembling the true rays, dif- 

 fering, however, in the plates, being a little smaller than the true radials, and being suc- 

 ceeded by five other smaller plates nearly in the same line. Between this series of anals 

 and each contiguous ray lies a series of three plates followed by two pairs. First inter- 

 supraradial hexagonal, surmounted by two pairs of smaller ones. The formula of this spe- 

 cies is, therefore, as follows : — ^ 



Basals 3 



Radials 3X5= 15 



Supraradials 2X2X5= 20 



Brachials 2X2X2X5= 40 



Regular Interradials 13X4= 52 



Azygos Interradials 30 



Inter-supraradials 5x5= 25 



Interbrachials 



Total plates in the cup 185 



One of our specimens is 3.4 inches long, to the bases of the arms. Another one, defec- 

 tive below, has a diameter of three inches at the bases of the arms ; most of the specimens 

 are not over half this size. 



There is a variety of this species (apparently) which is marked by ridges along the 

 series of radials and secondary radials. These ridges (in casts) are not interrupted by the 

 sutures. 



This massive species bears a remarkably close affinity with AcUwocrinus Christyi Hall, (No- 

 tice of Waldron Fossils, p. 2,) but it may be discriminated as follows : The first radial has a 

 height greater than its width, instead of being equal to it ; the second radial is higher than 

 wide, instead of the reverse ; the third radial is octagonal in the antero-lateral rays, and is 



