154 ECHINODERMATA PELMATOZOA SUB-KINGDOM in 



them twice as large as the other, and the two forming a knob-like body. E 

 five, their inner edges resting upon the angular margin of the basal disk ; they 

 spread broadly outward from the B, extending far beyond them. The two 

 larger R separated at the posterior side by two equal smaller plates ; and at 

 the anterior side by a single plate having a quite narrow upper face. M. 

 boletus, Schultze, apparently with fifteen arms ; their structure unknown. 

 Middle Devonian ; Eifel. 



Family 6. Calceocrinidae. Meek and Worthen. 



" Inadunata Monocyclica, in which a bilateral symmetry along the left anterior 

 radius and right posterior inter-radius has been superinduced in conjunction with 

 bending of the crown on the stem in such a way that the right posterior interray lies 

 along the stem ; with the left anterior, right posterior, and right anterior radials com- 

 pound ; with anal x (IRA) shifted over the right posterior radius, usually into the 

 right posterior interradius, and supporting a massive tube ; with three, rarely four 

 arms, of which two are as a rule peculiarly modified and bear armlets or pinnules." - 

 Rather, The Crinoidea of Gotland. Ordovician to Sub-Carboniferous. 



Castocrinus, Ringueberg. B distinct, all entering into the articular surface 

 of the stem. The right posterior, and right antero-lateral superradials 

 joined by ill-defined close suture, each abutting with one side on the 

 adjacent large simple R. The lower plate of the tube supported by the 

 right posterior superradial only, while the right antero-lateral superradial 

 supports the first brachial of the right antero-lateral arm. The right posterior 

 and right antero-lateral superradials separated from one another, and also 

 from the ventral tube, by the right posterior and right antero-lateral R. Arms 

 four. Ordovician ; North America. Type, C. furcillatus, W. R. Billings sp. 



Euchirocrinus, M. and W. B unfused, or perhaps sometimes the left pos- 

 terior fused with the left antero-lateral one. The right posterior and right 

 antero-lateral superradials fused in a T-shaped piece, which abuts with either 

 wing on the corners of the large simple R. The right posterior and right 

 antero-lateral inferradials separated from one another and from the tube 

 by the T-piece ; tube supported by the whole upper margin of the latter. 

 Arms three. Ordovician and Silurian ; North America. Type, E. punctatus, 

 Ulrich sp. 



Calceocrinus (Hall) Ringueberg. Left posterior B fused with the left 

 antero-lateral one ; the fused plates very rarely entering the stem articula- 

 tion. The posterior and right antero-lateral B bounded for some distance by 

 the large R. T-plate separated from the large simple R by the right 

 posterior and right antero-lateral R; it is low, wide, and occasionally very 

 small. Tube supported by the T-piece and the two inferradials to the right, 

 but not touching the two large simple radials. Arms three. Silurian and 

 Devonian ; Europe and America. Type, C. typus, Ringueberg. 



Halysiocrinus (Ulrich) Bather. B as in the preceding, but the fused 

 posterior and right antero-lateral ones never entering into the stem articula- 

 tion. T-piece either obsolete or concealed between the right posterior and 

 right antero-lateral inferradials, and the two large R in the stem articulation. 

 Tube supported by the inferradials to the right, which are in contact ; and 

 abutting by its lower corners on the two large simple R. Arms three. Bur- 

 lington and Keokuk Groups ; Mississippi Valley. Type, H. ventricosus, Hall sp. 



