CLARR III 



CRINOIDEA 



229 



Family 1. Bourgueticrinidae de Loriol. 



Column without terminal stem plate, but the distal portion of the stem bears very 

 numerous radicular cirri. It is slender, composed of joints which may be greatly 

 elongated with strongly concave sides, or about as long as broad with strongly convex 

 sides, or of any intermediate form ; but the articulating surfaces always consist of a 

 strong fulcral ridge {which may be interrupted in the centre by the central canal) 

 separaiing two large ligamental fossae ; one or more of the columnals immediately 

 Wilder the calyx may be discoidal,- mth plane surfaces. Dorsal cup small, but very 

 variable in size and in the relative proportions of its component plates ; composed of five 

 hasals (which may be solidly welded into a single plate), and {usually) five radials. 

 Infrabasals unknown, probably absent in the adult. Arms slender, five or ten ; if 

 the latter, two primibrachs are present. If there are four, six, or more radials, one 

 arm follows each radial. Cretaceous to Recent. 



Bourgueticrinus d'Orb. (Fig. 332). Basais not fiised. Radials five ; lower 

 brachials laterally connected. Proximal columnal round, as wide as the calyx 



Fig. 332. 



Bourgueticrinus ellipti- 

 cus Miil. White Clialk ; 

 Wiltshire. a, Calyx with 

 stem-joints, i/i ; 5, Ventral 

 aspect, enlarged ; c, Stem- 

 joints ; d, Articular sur- 

 face of stem -Joint ; e, 

 Girr US. 



Fig. 333. 

 Rhizocrinus pyriformis (Goldf.). Eocene ; Verona. 

 a, h, Calyx from one side (nat. size and enlarged); 



c, Same from above, with three of the Br in place; 



d, Median longitudinal section of calyx, Vi 5 e, Calyx 

 with slightly abraded outer surface, showing suture 

 lines between B and R ; f, Calyx with five rays, seen 

 from above (enlarged) ; g-k, Stem-joints, i/i. 



at its greatest breadth, those below it diminishing for one or two joints and 

 becoming compressed, with elliptical Joint faces, each columnal twisted so that 

 one end Stands at an angle to the other. ^ Cirri present distally, or perhaps in 

 middle of the stem. Cretaceous ; Europe and Alabama. 



Mesocrinus P. H. Carpenter. Proximale small and circular ; otherwise like 

 Bourgueticrinus. Cretaceous ; Sweden and Germany. 



(?) Dolichocrinus de Loriol. Radials form an elongate tube. Upper Jur- 

 assic ; Europe. 



Rhizocrinus Sars (Gonocrinus d'Orbigny, non Troost) (Fig. 333). Basais com- 

 pletely fused, forming a very large and elongate base ; radials very small, four 

 to seven (usually five or six) ; arms undivided ; column slender, composed of 

 greatly elongated segments of which the distal bear radicular cirri. Cretaceous ; 

 New Jersey. Eocene ; Europe. Recent ; north Atlantic. 



Bythocrinus Döderlein. Similar to Rhizocrinus, but with the basals separated 

 by distinct sutures ; radials (and arms) invariably five. Recent; in tropical 

 Atlantic, and western Indian Oceans. ,• i • i 



Democrinus Perrier. Similar to Rhizocrinus, but with the base subcylmdrical , 



