1881.] NATURAL SCIENCES OF PHILADELPHIA, 361 



instead of moderately developed underbasals, in not having the 

 first anal plate on a level with the first radials, and in the arms, 

 which in Glyptocrinus are composed of single joints, instead of 

 two rows of interlocking pieces as in Ghjptaater. Reteocrinus 

 differs in the size of its underbasals, the deeplj^ depressed inter 

 radial spaces, the irregular arrangement, and exceedingly large 

 number of interradial and interaxillar}- plates, and that the raj-s 

 are not connected laterally, but, all the waj' up from the basals, 

 separated by small interradial pieces. 



We propose for Glyptocrinus the following : 



Revised Generic Diagnosis. — Calyx obconical to subglobose, 

 its symmetry almost perfectly pentahedral. Surface ornamented 

 with radiating striae in form of elevated ridges, which divide into 

 numerous triangular impressed areas. The ridges passing along 

 the radial portions are rounded, nearl}' as wide as the arm joints, 

 and appear like arms that are soldered into the bod}'. The arms 

 rise verticall}' from the edge of the vault, forming undisturbed 

 continuations of the ridges of the calyx, and the higher radial 

 plates pass imperceptibly into arm plates. 



Underbasals five, rudimentary — perhaps sometimes obsolete — 

 entirel}^ hidden from view by the column, and filling only a small 

 portion of the basal concavity. Basals five, of uniform size, small, 

 scarcely extending to the sides of the bod}', slightly concave for 

 the attachment of the column. Primary radials 3X5, the lower 

 series somewhat larger, nearly similar in form ; the second 

 hexagonal ; the third pentagonal in outline, and supporting on 

 its upper sloping sides the secondary radials. The number of 

 secondary radials varies with the species, but, as a general rule, it 

 might be asserted, that in species with a third order of radials or 

 a second division within the body, there are only two secondarj^ 

 radials, while in species in which the second bifurcation takes 

 place in the free arms, their number is much greater. Species of 

 the latter kind sometimes have six, eight or more, and these are 

 succeeded to the last bifurcation bj' three, four or more free 

 plates. The tertiary radials, where they exist, are as variable in 

 number as those of the secondar}- order. There ma}- be within the 

 same species one, three or more of these plates soldered into the 

 body, or they all may be free plates, depending on the age of the 

 individual. 



Arms twenty, rising upright, almost verticallj' from the last 



