154 



THE CRINOIDEA 



Evidence for its truly Monocyclic nature is wanting; but in the 

 absence of proof to the contrary, it must be 

 left in this, apparently natural, position. The 

 stem is not unlike that of some Plicatocrinidae ; 

 the branching and syzygies of the unforked 

 arms remind one of the structure in the 

 arm-rami of Belemnocrinus and Saccocoma ; the 

 cup is not unlike that of Plicatocrinus Fraasi. 

 The only specimen at all complete is a male, 

 with testes probably mature and swelling out 

 in the proximal portions of the proximal 

 ramuli ; in these regions each ramular sup- 

 ports 2 or 3 square side-plates on either side, 

 and these support the covering-plates. The 

 orals could probably open to expose the 

 funnel-shaped gullet, which leads into a 

 narrow gut with single dextral coil ; glandular 

 ridges line the gullet and first part of the gut. 

 The intra-thecal connective tissue contains no 

 spicules. FAMILY 14. SACCOCOMIDAE. Mono- 

 cyclica Inadunata, in which 5 RR and a 

 minute centrale enclose a large spheroidal 

 thecal cavity ; each R has a prominent median 

 ridge ending in a narrow facet, which sup- 

 ports a thin arm, forking on IBr 2 ; beginning 

 at about IIBr J5 , each ramus gives off from 

 every 3rd Br unbranched alternating ramuli 

 arranged as in Hyocrinus ; the rami and 

 ramuli are usually found rolled up in their 

 distal portions ; Br cylindrical, elongate ; 

 lax and the more proximal IIBr may bear 

 lateral, paired, wing-like expansions, which 

 in the more distal Br and the ramulars are 

 always represented by delicate trellised pro- 

 cesses, with thicker upper and under mar- 

 gins, which it is conjectured supported a 

 continuous membrane ; no stem ; all skeletal 

 elements very thin and coarsely reticulate. 

 Genus Saccocoma, L. 'Agassiz (1834; syn. 

 Euryale, Konig), Solenhofen Lithographic 

 Fio. LXVII. Stone, Upper Jura (Fig. LXVIII.). Jaekel, 

 Hyocrinus bethel- who has admirably elucidated the structure 

 Chaito'cr ( Narra" and amnities of tJlis wonderfully specialised 

 tive, xf.) crinoid (1893), considers that .the arms were 



swimming-organs, the food-groove, ambulacral, 

 and genital systems being atrophied at their 

 distal ends, and that the animal was pelagic, 



floating in enormous swarms in the peaceful lagoons of Eichstadt and 



Solenhofen. 



