172 



ECHINODERMATA PELMATOZOA 



SUB- KINGDOM III 



on the ventral. Tegmen unknown. Upper Jura ; a rare form, found in the 

 Franconian and Swabian Alp. 



Hyocrinus, Wyv. Thomson (Fig. 288). This recent form is obviously 

 allied to the preceding, but differs from it rather conspicuously in the mode 

 of branching of its arms. It has a heavily plated tegmen, with mouth sur- 

 rounded by large orals. Carpenter regards it as the type of an independent 

 family. 



Family 7. Saccocomidae. d'Orbigny. 



Calyx small, hemispherical, non-pedunculate. Eadials five, very thin, elevated 

 ridges along the median line, and enclosing an extremely small basal 



Saccocomu pectinfita, Goldf. Upper Jura (Lithographic Slates) ; Eichstadt, Bavaria, a, Individual in natural 

 size ; 1>, Side view of calyx ; c, Calyx seen from below, 2/ x ; d, Two of the lower arm-plates ; c, Two arm-plates of 

 a higher order with one of the branches ; /, The upper part of one of the arms straightened out ; g, Lower 

 brachials of .S'. tenella, Goldf. (Figs, d and g greatly, the others slightly enlarged.) 



plate. Arms 5x2; thin, widely separated, and giving off alternately towards the 

 extremities - simple incurving branches. Arm-plates cylindrical; each side of the 

 ambulacral furrow lined ivith wing-like or spiniform projections. The entire skeleton 

 exhibiting a reticulated structure with coarse meshes. Upper Jura. 



The only known genus, Saccocoma, Ag. (Fig. 289), occurs profusely in the 

 Lithographic Slates of Eichstadt and Solenhofen, Bavaria. It is a free- 

 swimming form, whose affinities with the monocyclic Plicatocrinidae were first 

 clearly demonstrated by Jaekel. 1 



1 Zeitschrift der deutschen geol. Gesellsch. Bd. XLIV., 1892. 



