168 



ECHINODERMATA PELMATOZOA 



SUB-KINGDOM III 



rather heavy plates ; mouth and anus not observed. Arms uniserial, branching, and 

 bearing long pinnules. Column round to sharply pentagonal, without lateral cirri ; 

 the proximal joint the largest of the stem; distal end thickened and forming a stout 

 root. Jura, Cretaceous, and Recent. 



Apiocrinus, Mill (Figs. 279-281). Dorsal cup pyriform, supported by a 

 long cylindrical column, the proximal joints of which gradually expand in 



FIG. 280. 



Apiocrinus Parkinsoni, Schloth. Great Oolite; Ranville, Calvados. A, Diagram of calyx, showing course 

 of canals. These are represented by dotted lines when concealed within the plates, and by heavy lines where 

 visible on the inner surface of the basals. B, Median longitudinal section through the uppermost stem-joints, 

 showing empty space included between them ; b, Basal, seen from above and from the inside ; b*, Lower surface 

 of same ; ri, Radial, seen from without ; ri*, Inner aspect of same ; r2, and r%*, Corresponding views of first 

 brachial ; br, Arm-plates. (Canals are invisible in plates above the basals, except where they have become 

 exposed by weathering or abrasion.) 



FIG. 281. 



Apiocrinus Roissyanus, d'Orb. Upper Jura (Coral-Rag) ; Tonnerre, Yonne. Restoration (after d'Orbigny). 



diameter, so as to become of equal width with the B. Upper face of the 

 centrodorsal bearing five, low, angular ridges, which correspond in their dis- 

 position with the suture lines of the IB. Radials followed by two costals, 

 which are laterally and longitudinally united by rather close suture. Upper 

 faces of the costals excavated and striated ; the free brachials perforated, and 

 furnished with well-defined transverse ridges. In a few species small inter- 

 brachials are interposed between the costals. Column round, the proximal 

 joints in contact only near the periphery ; inner portions of the joints wedge- 

 shaped, and leaving a hollow space between them. Lias to Cretaceous. 



