230 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



the basals being separated by distinct sutures ; columnals very short, but 

 little longer than broad, more or less barrel or bead shaped ; radials (and 

 arms) invariably five. Recent ; tropical Atlantic and East Indies. 



Bathycrinus Wy v. Thomson {Illycrinus Danielssen and Koren ; Pterocrinus 

 Wyv. Thomson). Essentially similar to Bhizocrinus, but with ten arms, each 

 post-radial series dividing on the second ossicle ; basals usually much reduced, 

 forming a narrow ring beneath the much larger radials. Recent, chiefly occur- 

 ring at great depths, cosmopolitan. 



Monachocrinus A. H. Clark. Similar to the preceding, but with the basals 

 separated by distinct sutures, and usually nearly or quite as large as the 

 radials, sometimes larger. Lower Muschelkalk ; near Rovegliana. Recent ; 

 East Indies, Bay of Bengal, east Atlantic. 



Family 2. Phrynocrinidae A. H. Clark. 



Similar in general to the Bourgueticrinidae, but with the stem attaehed to a heavy 

 terminal stem-plate (dorsocentral) as in the Apiocrinidae. Recent. 



Here are placed the two genera Naumachocrinus and Phrynocrinus Clark, 

 occurring at depths of from 500 to 650 fathoms in the Pacific Ocean. The 

 former of these has a calyx superficially resembling that of Democrinus, but 

 composed of very small basals and much elongated radials. 



Family 3. Apiocrinidae d'Orbigny. 



Column without cirri ; enlarged distally and attaehed to a heavy terminal plate, 

 or fixed root ; composed of short ^ discoidal columnals having their articular faces 

 marJced with radiating Striae without fulcral ridge ; those next below the calyx often 

 increasing greatly in width, forming a proximal enlargement continuous with the sides 



of the calyx. In the more 



Fig. 334. 



specialised types the proximal colum- 

 nals may become penfagonal or 

 stellate, and may bear rudimenfary 

 cirri. Calyx variable, composed of 

 heavy plates. Infrabasals greatly 

 reduced, modified or fused with the 

 proximal columnal ; visible rarely 

 within the basal ring {cryptodicyclic). 

 Lower brachials more or less incor- 

 porated in the calyx by lateral union, 

 or by a few interbrachial plates. 

 Primibrachs two ; arms branching 

 regularly, usually more than once. 

 Jura, Cretaceous and Recent. 



Ran- 



Apiocrinus parlcinsoni Schlotheim. Great Oolite 

 ville, Calvados, a, Calyx and upper stem-joints, viewed froin 

 the side ; h, Ventral aspect ; c, Articular surface of one of the 

 stem-joints (natural size). 



Apiocrinus Miller (Figs. 334- 

 336). Plates of calyx greatly 

 thickened, especially at the distal 

 border of the radials, where the typical muscular articulation is modified 

 by an enormous enlargement of the dorsal ligamental fossa, consequent upon 

 such thickening ; thh expansion afFects in addition to the calyx, a series of 

 the Upper columnals, and of the lower brachials. Calyx in typical forms 



