1881.] NATURAL SCIENCES OF PHILADELPHIA. 3G9 



described as intermediate between fixed pinnule plates and radials. 

 This is but an abnormal case, but it gives some idea how in the 

 course of time, among species, bifurcating radials became devel- 

 oped from pinnule-bearing plates, and additional arms from the 

 proximal pinnules. 



Generic Diagnosis. — Form of calyx subturbinate or obconical ; 

 strongly depressed between the arm bases ; plates delicate, beauti- 

 fully ornamented with granules and stride, the radial portions 

 with strong ridges or costae ; anal area very wide, and hence sym- 

 metry distinctly bilateral. 



Underbasals five, small but not rudimentary, and generally 

 extending beyond the column. Basals five, four of them equal 

 with the upper side angular, the fifth larger with a truncate upper 

 side for the support of the first anal plate. Primary radials .3 X 5 % 

 width and height nearly equal, decreasing in size upward. The 

 third radials support two rows of secondary radials, which are 

 separated bj^ one to three interaxillary plates, the latter being 

 perhaps absent in young specimens. The number of secondary 

 radials, like in the Glyptocrinites^ is variable, differing amono- 

 species, and increasing with age in the individual ; their exact 

 number is rarely ascertained, as they pass gradually into brachials 

 and regular arm plates. 



Arms ten, simple ? and composed of two rows of interlocking 

 pieces with pinnules. 



Interradial areae large, and, compared with the preceding genera 

 composed of fewer and larger plates. There is one plate in the 

 first series, which rests between the two upper sides of two first 

 and between two second radials ; two in the second series, on a 

 level with the third radials, with much smaller plates above, which 

 connect with the interradial portions of the dome. 



Anal area distinctly wider. The first anal plate resting upon the 

 truncate posterior basal, and between two adjoining first radials ; 

 there are three plates in the second, and four or five in each suc- 

 ceeding series. Above the level of the third primary radials the 

 plates are bent somewhat inward, the anal area is in the middle 

 elevated into a low ridge, at the sides depressed. 



The vault which is only known in Glyptaster inornatus is 

 decidedly pentalobate, and resembles DoryciHnus in the anal 

 region. Anal opening excentric, protruding and reaching some- 

 what beyond the limits of the vault, not extended into a tube. 



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