Diadematoid Radioles. 
227 
wider lumen than usual in the species, and has in consequence been flattened. Differ- 
ences of lumen within the limits of one species may perhaps be correlated with 
different positions on the test; certainly, as between different species, the wider 
lumen is associated with the more pronounced Ornament, and, since this Ornament 
arises out of the internal structure of the stereom (PI. XVII, fig. 453), it is pretty 
clear that this association depends on the greater strength of the coarse striation, 
especially when enhanced by a cross-ribbing. However this may be, the time has 
not yet come for the suppression of C. Meyeri. 
With C. bicarinata it is another matter. Fresh evidence Supports Laube’s 
reference of this to C. linearis, although it must be admitted that he was not justified 
in making such a reference without examination of the holotype, and further that 
such examination might well have made him hesitate. The specimen figured by 
Klipstein (pl. xviii, f. 11) is No. 658 of his Collection (B. M. 36502); its shaft 
bears no trace of longitudinal Striae; in transverse section (fig. 434) one side of its 
shaft forms a curve of about 4 mm. radius, but with a tendency to a median angle, 
the other side a curve of about 1 mm. radius; where the two curves meet on 
each side is a slight keel that dies away at the proximal end of the shaft; there 
is a wide subcircular lumen filled with secondary calcite; the shaft is separated 
from the collerette by a slight but obvious ridge or terrace, which curves downwards 
so as to approach the annulus on the flattened side; the collerette is longitudinally 
striate, the annulus finely crenelate, and the acetabular margin smooth. This differs 
from C. linearis as diagnosed by Münster and by Laube in the absence of striae 
from the shaft, the presence of side-keels, the ridge defining the collerette, which is 
relatively long (Laube says of C linearis «collis brevis» and «sie gar keinen Hals 
hat»), the crenelation of the annulus, and the smoothness of the acetabulum. Very 
little weight is to be attached to the last two characters, and undoubted specimens 
of C. linearis vary in these respects. The few fragments of C. bicarinata which 
Laube had for study * must, one supposes, have shown the longitudinal striation or 
he would have noted its absence; at any rate the only other specimen in the British 
Museum (E 8535), a short fragment from St. Cassian, shows it plainly all over. 
On the other hand, this same fragment, though it appears to retain a portion of the 
base, has no trace of a collerette. In radioles that have longitudinal striae on the 
collerette but not on the shaft, it is relatively easy to distinguish the collerette; 
but in this species the limit between collerette and shaft is constituted only by the 
slight terrace, which marks the distal edge of the integument, and is only formed 
if that remains a sufficient time at the same level. The differences between C. 
linearis and C. bicarinata are therefore reduced to the flattened face and the slight 
lateral keels of the latter. The rarity of the bicarinate form is in itself an argument 
against its specific independence, and the evidence of the St. Cassian material would 
alone incline one to accept Laube’s action. Fortunately, strong confirmation is 
afforded by the Bakony specimens of a closely allied species, which is represented 
by cylindrical, compressed, and bicarinate forms associated at the various localities, 
some with and some without a collerette. 
Thus the seven or eight names with which this investigation began have been 
* Probably his pl. x, f. 10 b represents one of these ; a transverse section of it is represented 
on our Plate XIII, fig. 433. 
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