MELOCRINID^. 317 



surrounded by a circular ridge ; the arm bases slightly projecting. Surface 

 covered by numerous angular ridges^ which radiate from centre to centre of 

 the plates, producing various geometrical figures. The ridges connecting 

 the radials form a pentagon around the basal pit, which is radially disposed 

 and of which the sides support ^ve triangles, each one enclosing a smaller 

 one. The outer triangles, together with the pentagon, form a five-rayed 

 star, and the spaces between the rays of this star are also formed into tri- 

 angles, which are followed by other triangles above. 



Basals small, resting completely within the columnar depression. Radials 

 and costals of equal height, but the first costal narrower than the second. 

 The latter supports at one side an axillary distichal, followed by two small 

 palmars and two arms, and at the opposite side by two successive distichals and 

 a single arm, making three arms to the ray. Arms stout, biserial, not bifur- 

 cating at the lower ends; their upper parts unknown. Arm joints short, 

 with parallel faces. First interbrachial large, supporting a smaller, sub- 

 quadrangular plate, and three plates in the third row, which in turn are 

 followed by Rye cuneate plates, which extend above the level of the arm 

 regions. At the four regular sides, the three middle ones of these plates are 

 considerably larger than the outer ones, and touch the orals -, at the anal 

 side they are followed by a few additional plates, which abut against the 

 anal tube. Interdistichals small, consisting of three pieces, succeeded by 

 two interambulacral plates forming two slits. The number of slits at the 

 interradial spaces cannot be ascertained from the specimens. Ventral disk 

 slightly tumid ; the interambulacral spaces depressed, the plates almost flat, 

 the orals and radial dome plates, which are somewhat larger, covered with 

 small but sharp nodes. Anus subcentral. Column round, with crenulated 

 edges ; axillary canal pentangular. 



Horizon and Locality. — Hamilton group ; Alpena, Mich. 



Types in the Museum of the Davenport Academy of Sciences. 



Dolatocrinus glyptus (Hall). 

 Flate XXVI. Figs, ^a, h. 



1862. Cacabocrinus glyptus — Hall ; 15tli Rep. N. Y. State Cab. Nat. Hist., p. 140. 

 1881. Dolatocrinus glyptus — W. and Sp. ; Revision Palseocr., Part II., p. 135. 



Syn. Cacabocrinus glyptus, var. intermedius Hall; 1881, 15th Reg. Rep. N. Y. State Cab. Nat. 

 Hist., p. 141. 



Syn. Dolatocrinus ornatus Meek; 1871, Proceed. Acad. Nat. Sci. Phila., p. 57. 



