226 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



Dittmar non Billings) (Figs. 329-331). No anal x nor tube-plate visible. 



Calyx low, with base more or less concave. 



Infrabasals five, minute, concealed in the basal 



concavity, sometimes reduced to three, or atro- 



phied. Arms usually ten, exceptionally twenty; 



uniserial at their lower ends, but soon becoming 



biserial ; separate axial canal in radials, extend- 



ing into the arms. Tegmen not definitely 



known. Stern round, apparently without cirri. 



Abundant in the Trias, especially in the 



Muschelkalk of Germany. The stem fragments 



of E. UlUformis frequently form beds of marine 



limestone (Trochitenkalk). 



This genus was formerly associated by the majority 

 of European authors with the Recent Crinoids under the 

 Articulata. It was shown by Wachsmuth and Springer 

 that its relations are clearly with the later Paleozoic 

 Inadunata, and its position as such is recognised by 

 most recent writers. The type species, U. liliiformis, by reason of its striking appearance 



Fig. 329. 

 Diagram sliowing conr.se of axial canals 

 in the calyx and arms of Encrinus. Canals 

 represented by dotted lines when pene- 

 trating tlie interior of tlie plates, and by 

 heavy lines when exposed on the inner 

 side of the calyx (after Beyrich). 



Fig. 330. 



Eflicrinus liliiformis 

 Miller. Muschelkalk ; 

 Brunswick. 



Fig. 331. 

 Portions of the calyx and arms of Enorinus. a, Interior 

 of calyx ; ai, Exterior of same ; b, Basal, upper surface ; 

 r, Radial, inner surface ; ß, One of the uniserial, and ß*, bi- 

 serial arm-plates ; both of them traversed by duplicate 

 dorsal canals ; p, Pinnule ossicle (enlarged) ; br, First 

 brachial, under surface ; br^ 2, First and second brachials 

 joined togfether ; inside, seen from below ; br^, First brachial, 

 Upper surface, showing line of syzygial suture ; br"^, Second 

 brachial (axillary), showing articular facets. 



and beautiful preservation, early attracted the attention of observers. The generic name 

 was first applied in 1760 ; and the form is the best known of all fossil Crinoids, 



Order 4. ARTICULATA. J. S. Miller (emend. J. Müller). 



Tegmen coriaceous, studded with minute calcareous partides, which may l 

 invisible externally, or may he entarged into well-defined plates that rarely form a 

 complete investment. Mouth and food grooves exposed, but often hordered with one 

 or two rows of side and covering plates capahle of heing closed down over them. 

 Orals present in the young, often also in the adult. Plates of the dorsal cup, except 



