I30 SMITHSONIAN INSTITUTION 



collection from Grimsby contains about the same number. The Hall collection in the Amer- 

 ican Museum has about a half dozen. By a selection of specimens from these collections, and 

 a few obtained by me from other sources, we are enabled to illustrate the species in great 

 variety as to form and maturity. Most of them are flattened by pressure and give a wrong 

 impression of the true outline. A few, such as figures 17 and 18 on Plate III. are undistorted 

 and show the correct figure, which is an elongate ovoid with the widest part above the upper 

 primibrach, and a relative height to width at that level of about 1 to 1.1. Many measure- 

 ments and calculated diameters yield about the same general average in form and propor- 

 tions ; and observation of about 40 specimens shows no variation in the normal number of two 

 primibrachs, but variation from three to four among the secundibrachs. The radial is a large 

 plate, of more than the combined height of the three succeeding brachials — a proportion which 

 differs considerably in different specimens. 



On comparing the young with the mature specimens a great difference is observed in 

 the development of the arms. In a full-grown specimen (PI. Ill, fig. 10) three bifurcations 

 are in view; those of medium size (figs. 17, 18) show but two; while in a very young indi- 

 vidual there is but one (figs. 15, 16). This juvenile character in the brachials becomes con- 

 stant in another species, as will be seen farther on. The axial canal in the column is rounded 

 or obscurely pentangular, but at the inner surface of the infrabasals it enlarges into a trian- 

 gular opening, bounded by a low rim, with the angles directed to the middle of the infrabasal 

 plates (PI. Ill, figs. 6a, b) ; this is similar to the structure seen in Forbesiocrinus and 

 Ichthyocrinus. 



I have figured three of Hall's types from the American Museum. His figure la (Nat. 

 Hist. New York, Pal., vol. 2, pi. 45) is incorrect in the drawing of the arms above the first 

 bifurcation, where it shows only a single secundibrach. The divisions of the higher brachials 

 are not always easily observed in the specimens as found, and these details were not thought 

 so important at that time. Similar errors appear in his figure lb, where the left posterior ray 

 is incorrectly made to show three primibrachs ; but in Hall's description the facts are cor- 

 rectly stated 



Ringueberg's L. puteolus is probably a calyx of this species injured by parasites. Hall's 

 Lecanocrinus simplex (op. cit., 1852, p. 202, pi. 46, figs. 2a-e), is doubtless a very young 

 Ichthyocrinus, and the figures as to details of base and surface ornament are probably not 

 strictly correct ; the specimen cannot be found, but I have figured two similar ones under 

 Ichthyocrinus laevis. 



Types. In the American Museum of Natural History, New York. The original of 

 Plate III, figure 7, is in the University of Toronto ; the other specimens figured are in the 

 author's collection. 



Horizon and locality. Silurian, middle third of the Rochester shale ; Lockport, New 

 York, and Grimsby, Canada. It has not been found in the equivalent Osgood formation, nor 

 in the Waldron shales of Indiana and Tennessee. 



Lecanocrinus solidus Ringueberg 

 Plate III, fig. 19 



Lecanocrinus solidus Ringueberg, Bull. Buffalo Soc. Nat. Sci., I, 1886, p. 8, pi. 1, fig. 4. 



A large species. Crown elongate, pyriform ; height to width at IAx, 1 to 

 1.1 ; base narrow, its side outline continuous with the column, and concave for a 

 short distance. Surface smooth. Height of crown, 30 mm., width at IIBn, 

 18 mm. ; column facet, 5 mm. 



