58 
Trias sic Echinoderms of Bakony. 
Isocrinus ? sp. 
(Plate V. fig. 127). 
Material. — A brachial from Cserhät (Leitnerhof). Cassian age. 
Description of Specimen. — The outline is approximately circular, 
but not bilaterally symmetrical. 
The ventral groove is narrow, V-shaped, and confluent with the axial canal, 
which is traceable as a slight enlargement of the apex of the groove. 
The two articular surfaces are dissimilar. One extends almost to the periphery, 
and is rather rough, perhaps owing to weathering. The groove slopes downwards 
to the left, so that the right-hand half is the larger. The surface swells up around 
the apex of the groove in two confluent knobs which form a rudimentary fulcrum. 
The left-hand shoulder passes almost imperceptibly into the side of the ossicle and 
presents no depressions or ridges. On the left side the wall of the groove is about 
at right angles to the joint-face. The right-hand edge of the groove is bevelled, 
the slope becoming wider towards the upper angle of the brachial. Next the edge 
of this slope is a slight triangulär depression, also widening towards the upper 
angles of the brachial. The right shoulder is slightly bevelled. From this bevel an 
obscure rim bounds the dorsal or lower edge of the joint-face. 
The other articular surface is smaller; the sides of the brachial curve inwards, 
so that the boundary of the face lies about half-way between the periphery and 
the ventral groove. In accordance with the asymmetrical slope of the groove, the 
larger half both of brachial and of joint-face is on the left-hand side. The face is 
excavate, sloping from the boundary downwards to the groove in a gentle curve. 
The upper right-hand edge of the groove has a straight bevel similar to that seen 
on the other face, but oblong instead of triangulär. Outside this bevel is a flat 
bevelled surface sloping in the other direction and almost continuous with the 
general curve of the side of the brachial. This outer bevel may be a facet for a 
pinnule. Immediately around the apex of the groove the surface is slightly depressed, 
perhaps to receive elevations like those seen on the other face. 
Total height along dorso-ventral axis.2"6 mm. 
Greatest width ..2‘7 » 
Greatest thickness.IT » 
Depth of ventral groove . ’.1*2 » 
Relations of the Specimen. — The joint-face first described appears to 
be that of a normal brachial. The triangulär depression on the right of the ventral 
groove was probably the muscle-fossa, while the slight depression within the dorsal 
rim was for the reception of the dorsal ligament. The interarticular ligament was 
probably diffused over the surface around the fulcral elevation. The other excavate 
joint-face, though less clearly marked, cannot have been syzygial if the outer bevel 
represents a pinnule-facet; the inner bevel, on the right of the ventral groove, was 
perhaps for the attachment of the ventral muscle on that side. 
The surfaces therefore present no features which forbid the reference to 
Isocrinus, although they are distinctly primitive in the slight differentiation of ridges 
and fossae, and, above all, in the confluence of the ventral groove with the 
axial canal 
