200 Mr. F. A. Bather on British Fossil Crinoids 



The Stem attained a length of at least 11 centim. It was 

 round in section, with a width 

 (in 57048) of about 4-5 millira. 

 In the proximal region it is com- 

 j)osed of ossicles of three sizes, 

 the larger ones slightly pro- 

 jecting, with an average height of 

 •4 niillim. (zincotype, tig. 5). In 

 the more distal regions (fig. 10) the 

 ossicles are smooth and more equal 

 in height. The sutures are crene- 

 late, indicating radiate strife on 

 the articular surface. The lumen 

 is small, as in Botri/ocrinus, and 

 from it there proceed five radial 

 sutures, which are usually visible 

 on the outside right up to the 

 dorsal cup. In the distal region 

 of the stem the pentaraeres show 

 only a slight tendency to the 

 hexagonal shape and semi-alter- 

 nating arrangement described for 

 Botryocrinus. The distal most 

 end of the Cambridge specimen Fig. lO.-Di.tal part of Stem in 

 is smooth and rounded, and this the larger Dudley Museum 

 though the whole stem and cup specimen of M. hreus. ( x 

 are very slightly disturbed. If '^a diam.) 

 this rounding be due to weathering, it would appear to 

 have been accomplished while the creature was yet alive. 

 (PI. XI. fig. 3.) 



General Remarks on the Genus. 



In the composition of its cup, in the anal area, and in the 

 simple dichotomy of its arms, this species resembles the species 

 of Cyathocrinus^ and, were that genus not more strictly defined 

 than it has hitherto been, it would doubtless be referred 

 thither. On the other hand, there are many points, not 

 hitherto recognized as of great importance, in which the 

 present species resembles a very diflerent assemblage of 

 Crinoids. The shape of the cup, esfiecially of the radials, is 

 the same as that of Jiotryocrinus. The ventral sac is of the 

 same structure as that of Dendrocrinus, Jjotryocrinus, and 

 Thenarocrinus) while the general resemblance of the smaller 

 Dudley specimen to the type specimen of T. yracilis (Brit. 

 Foss. Crin. IV., * Annals,' ser. 6, vol. vii. pi. i. fig. 4) cannot 

 pass unnoticed. The arms arc especially like those of T. 



