^^ 



178 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Reteocrinus StellariS Billings. 

 Plate IX, Figs. 3a, h, c, 



1859. E, Billings; Geol. Rep. Canada, Decade IV., p. 64, Plate 9, Tigs. 4^, b, c. 



1877. S. A. Miller; Catal. Amer. Palseoz. Eoss., p, 90. 



1881. W. and Sp. Revision Palseocr., Part IL, p. 193. 



1889. S. A. Miller; North Amer. Geology and Palseout., p. 277. 



Calyx proportionally larger than in any other species of the genus, 

 embracing all the distichals and portions of the palmars. 



Infrabasals and basals unusually large ; the former projecting distinctly 

 beyond the column, each plate forming a good-sized pentagon. Basals 

 heptagonal, slightly truncated and folded inward at the upper ends; four 

 of them of equal size, that facing the anal side larger, and the truncation 

 wider. The surface of the basals is marked by prominent keel-like pro- 

 cesses, meeting in the centre of the plates ; one of these proceeds to the 

 radials and costals, two others to the infrabasals. At the sides of the pro- 

 cesses there are deep depressions, five of them in a radial direction, formed 

 by the inflection of the lower angles of the radials and the upper lateral 

 margins of the basals ; five others, somewhat smaller, triangular in outhne 

 and interradial, by the basals and infrabasals. The posterior basal, at its 

 upper face, has three ridges instead of two, of which the median one is 

 continuous with that formed by the anal plates. Eadials about one half 

 longer than the costals. Costals three ; the first and second quadran- 

 gular, the third pentangular. Distichals five to seven or more, decreas- 

 ing in width upwards, the upper ones taking the form of free arm plates. 

 Above the distichals are two more divisions, but only a few^ of the palmars 

 take part in the calyx. The arms are extremely short, and taper rapidly ; 

 they are composed of rather long, quadrangular joints. Interbrachial and 

 interdistichal areas profoundly depressed, paved by numerous irregularly 

 arranged and ill-formed pieces, with a slightly stellate surface. Anal in- 

 terradius twice as wide as the others ; divided by a longitudinal row of anal 

 plates, somewhat narrower than the costals, but resembhng them in height 

 and curvature. Construction of tegmen, position of anal opening, and 

 arrangement of pinnules unknown. Column obscurely pentangular, at the 

 upper end composed of very thin, knife-like joints. 



Horizon and Locality, — Trenton limestone ; City of Ottawa, Ontario, 

 Canada. 



Our figures were made from the ty;pe specimens in the Canada Survey 

 Museum. 



