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 l)y Goldfuss as Pentacrinus 

 scnlaris ; ^ while they are certainly absent externally in one of the two known specimens of 

 Metacrinus costatus, though fully developed in the other (PI. 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 arc so greatly reduced in size as to fail to appear externally, 

 as occasionally happens in Encrinus and in the fossil Comatulaj, which retain their 

 embryonic basals in an unmctamorphosed condition.^ They are sometimes quite small 

 and insitrnificant in comparison with the radials, as in the Liassic Pentacrinus tuherculatus, 

 and in some varieties of the recent Pentacrinus decorus (Pis. 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 

 (PI. 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 

 (PI. XIII. fig. 1 ; PI. XV. fig. 2) ; while the union of their inner ends is more extensive 

 PI. XII. fig. IG ; PI. 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 hlahei a.m\ Pentacrinus decorus (Pis. XXXI., XXXV.) to that oi Pe^itacrinus 

 tvyvllle-thomsoni and Pentacrinus maclearanus, in which the radials are separated from 

 the top stem-joint by a ring of large and closely-united basals (Pis, XVI., XIX. figs. 1, 

 G, 7). The genus Cainocrinus of Edward Forbes has been lately revived by de Loriol^ 

 for a few fossil species which possess a closed basal ring, but are not otherwise different 

 from Pentacrinus. The condition of the recent Pcntacrinida), 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 Comatulfe, in 

 which group there appears to be much more individual variation than among the 

 PentacrinidjB. 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 Schluter* 



1 Petrefacta Germaaije, vol. i. pi. Ix. fig. 10. 



2 On the genus Solanoorinus, Goldfuss, and its Relations to recent Comatulse, Journ Linn. Soc. Land. ZooL, vol. 

 XV. pp. 211, 212. 



^ Swiss Fossil Crinoids, pp. Ill, 112. 

 Ueber einige astylide Crinoiden, Zeitschr. d. deutsch. geol. Gesellsck, 1878, p. 66. 



