Echinoid Jaw-fragments. 135 
Cserhdt (Leitnerhof) (a & b). 
(Plate IX., figs. 241—244.) 
Two rotulae. Cassian. 
a is the smaller and better preserved. (Figs. 241, 242). 
b, which is about twice as large as a, has lost one end. (Figs. 243, 244). 
ais 38 mm. long, 1°8 at widest part. Its under surface (fig. 241) appears simpler 
than that of Cidaris papillata as figured by Loven (Echinologica 1892, fig. 44), especially 
as it is not easy to distinguish the interior and exterior foveae. There is, however, 
an obvious eminence about the middle of each side, doubtless for the attachment 
of the musculi rotulae exteriores. There is a distinct median ridge. The upper 
surface (fig. 243) is gently rounded. 
b is broken at the exterior or condylar end. It is 6°8 mm. long and 2°9 mm. 
at its widest part. The under surface (fig. 243), though devoid of the median ridge seen in 
a, appears to show both the foveae, although the exterior one is rendered indistinct 
by the above-mentioned fracture. It also shows an eminence for the musculi rotulae 
exteriores. The rotula is somewhat curved in the direction of its length, the conca- 
vity of the curve being uppermost. The upper surface (fig. 244) is rounded, and the 
excavation for the inner end of the compass is more marked than in a. 
Obviously a and 6 are of distinct species. 
The Radioles. 
Terminology. — The terms employed are shown by the annexed diagrams. 
Rachis Vane 
‘ 
MS 
Adapical 
Outer face 
Blade 
RHE 6 5 
Handle 
Colleretie Inner face 
Adoral 
Text-fig. 11. Diagrams showing terminology of Primary Radioles. 
The term radiolus (Anglicé: radiole) was proposed by Desor, and its English use 
has been sanctioned by P. Martin Duncan, W. P. StapeENn, and J. W. Grecory. Shaft is 
the equivalent of the French tige, and the German Stiel oder Kérper. The shaft is sometimes 
divisible into handle and blade, sometimes into rachis and vanes. Collerette 
equals the German Stachelhals. Annulus corresponds to the French anneau, the German 
Ring. Base is called by French writers bouton ou téte, by German writers Stachelkopy. 
Acetabulum was used by SLapen in Eastman’s translation of ZirreL’s Grundziige 
