ICHTHYOCRINIDAE 309 



The relation of these parts is better shown by the cross-section, figure 5<f. In the other 

 specimen, 6a, b, c, the cavity is nearly as deep and relatively wider. The latter has one good- 

 sized interbrachial, as usually found throughout the genus, but 5a-c, although a mature speci- 

 men, has no semblance of such plates nor space for any — the rays abutting closely on a 

 straight line. These are the only specimens known, so that we do not know which form is the 

 more prevalent in the species ; but it is evidently a similar case to that of W achsmuthicrinus 

 thiemei, in which interbrachials are present or absent irrespective of stages of growth. 

 Schultze defined the species upon the specimen without interbrachials, and proposed for the 

 other one the variety interscapularis; but in view of the high specialization of the forms in 

 other characters it does not seem advisable to separate them. 



In Schultze's diagram of the species (op. cit., p. 39, fig. 6), and his figure of the first 

 specimen (ibid., pi. 7, fig. 2a), some large anal plates are erroneously shown; the anal plates 

 in both specimens are mostly gone, and through the space occupied by them may be seen in 

 one place part of the wall of the inward projecting basal cavity. The species has small 

 ramules, and few of them; in its short, non-spreading crown it is closer to D.' concavus than 

 to any other species. 



Types. Museum of Comparative Zoology, Harvard College. 



Horizon and locality. Middle Devonian, Eifel limestone (Stringocephalen-Kalk) ; 

 Kerpen and Steinfeld, Eifel, Germany. 



Dactylocrinus concavus (Rowley) 

 Plate XLI, figs. 7-0 



Ta.rocrinus concavus Rowley, Amer. Geologist, XII, 1893, p. 304, pi. 14, fig. 2. — Ibid., XIII, 1894, p. 153, 



figs. 3, 9, 10 on p. 151. 

 Aristocrinus concavus Rowley, Amer. Geologist, XVI, 1895, p. 217, figs. 1, 2 on p. 220 ( ? Callaway crinus 



on p. 219). — Keyes, Bull. Geol. Soc. America, XIII, 1902, p. 285. — Greger, Amer. Jour. Sci., XXVII, 



May, 1909, p. 376. 



A rather small species. Crown short, rotund, with broad base ; contracting 

 above I Ax, where height to width is I to 2.2; spread of calyx from outside of 

 basal rim, 1 to 2 ; cross-section obtusely pentagonal, side outline curved. Base 

 broadly and shallowly concave, resting on basals and lower incurved points of 

 radials. Surface smooth. Crown of mature specimen, 25 mm. high by 22 mm. 

 wide ; base at line of curvature of rim, 1 1 mm. ; column facet, 5 mm. 



IBB small, wholly covered by the column. BB curving from basal cavity 

 to outside of rim; their points visible in side view; post. B truncate, not rising to 

 top of RR, followed by small anal x, and this by two series of 3 or 4 plates taper- 

 ing to an apex between posterior rays. iBr one very large plate, rising to top of 

 IIBri, with a wide, rounded, distal face, probably for attachment of perisome. 

 illBr present in large specimens. RR unusually large for the genus — the larg- 

 est plates in the calyx. IBr much shorter and narrower. Rays and their divi- 

 sions deeply rounded, tapering but little; the inner branch the smaller; IIBr 

 usually 3, occasionally 2 or 4. Ramules small, 4 to 6 visible below point of in- 

 folding; intervals usually of 3 or 4 brachials, shorter in the distal portions. 

 Column small, with thin ossicles next to calyx. 



