REPORT ON THE CRINOIDEA 35 
any notice of its peculiarities. They likewise appear to be absent in the Forest-Marble 
specimen from Farley in Wiltshire, which was described by Goldfuss as Pentacrinus 
scalaris ;* while they are certainly absent externally in one of the two known specimens of 
Metacrinus costatus, though fully developed in the other (Pl. XLIX. figs. 1, 2). This is 
a most curious anomaly; but as the specimen cannot be sacrificed to investigation, it is 
impossible to ascertain whether the basals are absent entirely, or whether they have been 
metamorphosed into a rosette. 
It is possible that they are so greatly reduced in size as to fail to appear externally, 
as occasionally happens in Hnerinus and in the fossil Comatule, which retain their 
embryonic basals in an unmetamorphosed condition.? They are sometimes quite small 
and insignificant in comparison with the radials, asin the Liassic Pentacrinus tuberculatus, 
and in some varieties of the recent Pentacrinus decorus (Pls. XXXIV.-XXXVL). In 
these and similar forms they appear at the lower angles of the calyx as minute rounded 
plates, between which the lower edges of the radials rest directly upon the top stem- 
joints. The basals are therefore only in contact with one another by their inner ends 
(Pl. XXXIV. fig. 8). But in other species, both recent and fossil, they are considerably 
larger, and their outer ends separate the radials more completely from the top stem-joint 
(Pl. XIII. fig. 1; Pl. XV. fig. 2); while the union of their inner ends is more extensive 
Pl. XIL fig. 16; Pl. XXVI. fig. 11). In fact all degrees of union may be traced (both 
in different species and in different individuals of the same species) from the condition of 
Pentacrinus blaker and Pentacrinus decorus (Pls. XXXI., XXXV.) to that of Pentacrinus 
wyville-thomsoni and Pentacrinus maclearanus, in which the radials are separated from 
the top stem-joint by a ring of large and closely-united basals (Pls. XVI, XIX. figs. 1, 
6, 7). The genus Caznocrinus of Edward Forbes has been lately revived by de Loriol 3 
for a few fossil species which possess a closed basal ring, but are not otherwise different 
from Pentacrinus. The condition of the recent Pentacrinidee, however, is such as to entirely 
preclude the possibility of employing this very variable character as a generic distinction. 
A similar series of gradations is to be met with among the fossil Comatule, in 
which group there appears to be much more individual variation than among the 
Pentacrinidz. In some few species no basals are visible externally at all. In others, 
the outer ends of small prismatic rods may appear at some angles of the calyx but 
not at others, while their inner ends do not meet at all or only very slightly so. In 
some species again, the outer ends of the basal rods are smaller than the inner ends, 
which meet together and entirely separate the median portion of the radial pentagon 
from the centro-dorsal beneath, Lastly, in a chalk Comatula mentioned by Schliiter* 
1 Petrefacta Germaniz, vol. i. pl. lx. fig. 10. 
2 On the genus Solanocrinus, Goldfuss, and its Relations to recent Comatule, Journ Linn. Soc. Lond. Zool., vol. 
xv. pp. 211, 212. 
3 Swiss Fossil Crinoids, pp. 111, 112. 
Ueber einige astylide Crinoiden, Zeitschr. d. deutsch. geol. Gesellsch., 1878, p. 66. 
