140 PROCEEDINGS OF THE ACADEMY OP [1886. 



basals. In addition to Walcott's typical species, we refer to 

 3Ierocrinus: Dendrocrinus curtus Ulrich. 



Generic Diagnosis. Dorsal cup very small ; short and extend- 

 ing laterall}^ but little beyond the periphery of the upper stem 

 joint. 



Underbasals five, comparatively large, seen distinctly in a side 

 view. Basals short, all hexagonal ; alternating with four of the 

 radials and the az3'gous plate, which all are of similar form, pen- 

 tangular, wider than long. The four radials support upon their 

 truncate upper face a row of brachials, the az3'gous plate from 

 the same level the fifth radial. The right posterior radial has 

 the same form as the azj'gous plate, but, while the latter is 

 angular below, the radial has an angular upper side, giving off 

 toward the left the ventral tube, and toward the right a row of 

 brachials. There are generally six or more brachials to each 

 ray, composed of short quadrangular pieces, except the upper 

 which is axilla^3^ Arms long, bifurcating ; without pinnules ; 

 tapering toward the tips ; composed of quadrangular joints. 

 The bifurcations take place at regular intervals, and both arms 

 of the same division are of equal size. 



Column round, very strong, composed of unusually narrow 

 joints. 



Locality^ Position, etc. Lower Silurian of America. 



*1879. Merocrinus curtus (Ulrich), Dendrocrinus curtus, Cincin. Soc. Nat. Hist., 

 vol. ii (April), PI. 7, fig. 14. Utica shale. Cincin., 0. 



1883. M. corroboratus Waleott, Adv. sheet 35th Rep. N. Y. St. Cab. Nat. Hist., 

 p. 4, PI. 17, fig. 6. Trenton limest. Trenton Falls, N. Y. 



1883. M. typus Waleott, Ibid., p. 3, PI. 17, fig. 5. Trenton limest. Trenton Falls, 

 N. Y. 



CARABOCRINUS E. Billings. 

 (Revised by W. and Sp.) 



1856. E. Billings, Rep. Geol. Surv. Canada, p. 275. 



1859, E. Billings, Ibid., Decade iv, p. 30. 



1879. W. and Sp. Revision I, p. 143. 



1881. Walter R. Billings, Trans. Ottawa Field Natur. Club, p. 34. 



In Part I of this Revision we placed Garabocrinus among the 

 doubtful genera. It was founded by E. Billings upon certain 

 peculiarities among plates of the azygous side, resembling other- 

 wise closely Gyalhocrinus. When Billings proposed the genus, 

 the azygous side had been observed only in a single specimen, 



