MELOCRINIDE. 279 
A small species. Dorsal cup obconical with slightly convex sides ; 
section across the costals sharply pentagonal, owing to the conspicuous radial 
ridges, which pass from the arms down to the centre of the radials, where 
they divide and are continued to the basals. The ridges, which are rounded, 
grow narrower toward the middle of the plates, widening at their margins. 
Surface, except along the ridges, covered with numerous small pustules 
without definite arrangement. 
Basals large, forming a pentagonal cup with a rim around the bottom. 
Radials twice or nearly three times as large as the second costals; the first 
costal larger than the second. Distichals free beyond the fourth plate; the 
first and second considerably the larger; the second one pinnule-bearing, 
and also the fourth (not the third), which is slightly wedge-shaped, and con- 
siderably smaller than the preceding ones; from the fifth to the eighth, the 
plates are decidedly cuneate, the higher ones interlocking. Arms 10, simple 
throughout; thin, composed of two series of trigonal pieces. Interbrachials: 
1, 2, 2, efe.; the plates large. Anal side slightly wider; the first plate 
a little larger than the corresponding ones of the other sides; the succeed- 
ing pieces comparatively smaller; there are three plates in the second row, 
and in all the rows above. The plates of the median series are formed into 
a conspicuous longitudinal ridge, which divides on the first anal plate, send- 
ing a branch to the middle of adjacent radials. Nothing is known of the 
structure of the ventral disk and anal opening, and nothing definitely of the 
column, 
Lorizon and Locality. — Black River limestone ; Renfrew Co., Canada. 
Type in the Canada Survey Museum at Ottawa. 
Remarks. — The large columns which E, Billings figures from the Tren- 
ton group of Ottawa, and which he thought might be referable to G. priscus, 
probably belong to a different species. 
STELIDIOCRINUS Awncetin (Restricted by W. and Sp.). 
1878. Ancxtin; Iconogr. Crinoid. Suec., p. 21. 
1879. Zirren; Handb. der Paleont., Vol. L., p. 345. 
1881. W. and Sp.; Revision Paleocr, Part IT., p. 98 (Proceed. Acad. Nat. Sci. Phila., p. 272). 
1885. W. and Sp.; ibid., Part III., p. 102 (Proceed. p. 324). 
Calyx small, subturbinate, plates smooth; interradial areas depressed ; 
radial plates elevated but not ridged; ventral disk composed of but few 
plates. 
