on 
(op) 
Triassic Echinoderms of Bakony. 
Isocrinus? sp. 
(Plate V. figs. 123126) 
Material. — A patina from Cserhat (Leitnerhof). Cassian age. 
Description of Specimen. — This consists of five radials and five basals. 
In a side-view of the patina (fig. 123) the basals reach upwards to more than 
half its height. They are rounded and swollen so as to project very slightly beyond 
the radials; the most prominent part of each basal is between its two upper angles. 
Below they curve inwards and upwards, forming a deeply hollowed base (fig. 124), 
which was filled with matrix. After the extraction of the matrix there were visible 
no traces of infrabasals, but the interbasal sutures were seen to stretch right up 
and, apparently though not quite certainly, as far as the radial angles of a small 
pentagonal opening. At a slight distance from this opening the basals bend a little 
more sharply, thus producing a faint circular depression, perhaps the stem-facet, 
but with no trace of striae. 
The radials are swollen, but not so rounded as the basals. The most pro- 
minent part, or umbo, of each radial, lies between the two lower angles, or a little 
below that level; from here the plate slopes inwards to the margin of the facet, 
forming a rather flatter subtriangular surface, the edges of which run from the 
umbo to the shoulders of the radial, which is rather narrower above than below. 
The facet then bends abruptly inwards. The combined facets and muscle-plates 
of the radials form an approximately horizontal surface at the top of the patina, 
with but a small central concavity. The details of this surface (fig. 125) are not 
very clearly seen, since the specimen has been somewhat rolled or weathered. The 
fulcral ridge faces outwards, with a nearly straight outer or dorsal margin; it 
contains an oval axial canal with the long diameter parallel to the ridge. The 
dorsal ligament-fossa is a smooth depression. From the middle of the fulcral ridge, 
at a little distance from the axial canal, a slight groove extends to the central 
cavity, deepening as it goes; it is bordered on each side by a very Slight ridge, 
parallel with it. Outside these ridges, and next the fulcral ridge, on each side, is a 
triangular depression, presumably for the interarticular ligament. On this assumption 
the muscies were attached to the more adcentral regions of the facet — the muscle- 
plates; but no fossae or striae are distinguishable. 
Greatest diameter of patina, at basal and radial umbones. . 40 mm. 
Greatest height of -patina® <).:3) 415 s2iusepsues) Er rou ene 
Height; fy basalsy 21 ¢~ | (elo. to. Lee Glee Satan ee ee 1°99 to, 2:1, > 
Width of ibasalse. fen.) oe<y er See eden ee eee Owl ee 
Height “of jradials-.. 5. sabes “Agen ss He elas ewes, ceeeCincapelstaaae. 
Width of radials below . 5. 2. . 5 = oe S# omcauaslos 
Width, of radials) above. ).):5 92) spatiy-s) | dips ee econ Ones 
Width; of ‘basal .excavation: «-<) .; 2° h_-=)) dikes Cie a Oe 
Relations of the Specimen. — The preceding account agrees fully with 
the reference of the patina to Isocrinus. The absence of infrabasals, the general 
shape, and the details of the upper surface preclude a reference to the Encrinidae. 
The absence of infrabasals shows that the specimen does not belong to Dadocrinus, 
