REPORT ON THE CRINOIDEA. 343 
to receive the wide basal joints of the cirri ; so that its re-entering angles are deeper than 
those of an ordinary internodal joint (compare Pl. XXXIX. figs. 8, 9; and Pl. LIM. 
figs. 2, 4). The infra-nodal joints, however, are less deeply incised than those of Penta- 
crimus, and are sometimes not modified at all, as in Metacrinus interruptus and 
Metacrinus rotundus. This is the case in Pentacrinus wyville-thomsoni (Pl. XIX. 
figs. 3, 4), in which the lower edge of the cirrus-socket of the nodal joint projects out- 
wards beyond the level of the infra-nodal joint below it, while the supra-nodal is only 
slightly modified to receive the bases of the upward projecting cirri. Traces of a similar 
rim at the lower edge of the cirrus-socket are to be seen in Metacrinus interruptus 
(Pl. LIL. fig. 2). 
I know of no eharacters by which isolated internodal joints of Metacrinus can be 
distinguished from those of Pentacrinus, the relations of the teeth to the petaloid sectors 
being the same in both types. But the number of internodals is much more constant 
in Metacrinus than in Pentacrinus. In the latter genus there may be only one or two, 
as in Pentacrinus maclearanus (Pl. XVI. fig. 1); or about sixteen in Pentacrinus 
asterius (Pl. XI.), and about forty in Pentacrinus wyville-thomsoni; whereas in Meta- 
crinus the limits of variation are from six or seven in Metacrinus wyvillii (Pl. XLVIIL) 
to thirteen in Metacrinus murrayi (Pl. XLIL); so that this character is of less value in 
the classification of the species than it is in Pentacrinus. 
The geographical range of Wetacrinus is much more limited than that of Pentacrinus. 
Neither genus has been found in the Pacific east of long. 170° W.; but there are no 
Atlantic species of Metacrinus. Pentacrinus was obtained without Metacrinus at 
Stations 171 and 175 in the South Pacifie; while Metacrinus occurred alone at Station 
209 (among the Philippines), and also in considerable abundance and variety at Station 
192, in the Arafura Sea. It extends as far west as Singapore, and is represented by two 
species in Japanese waters, where no Pentacrinus is known, excepting the doubtful 
Pentacrinus mollis (Pl. XXXII. figs. 7-10), On the other hand, Metacrinus has not 
been met with below 630 fathoms, while Pentacrinus has been dredged at 1095 fathoms 
in the Atlantic, and 1375 fathoms in the Pacific Oceans. 
The mutual relations of the thirteen species of Metacrinus in which the calyx is 
known, are shown in the following Table. The Challenger species are numbered 1 to 
11, and the letters P. H. C. are appended to those which I have recently described 
in the Transactions of the Linnean Society. The “Vega” specimen, which concludes the 
list, has not yet been described. There are two other species of the genus (one obtained 
by the Challenger) which are known as yet only by the characters of their stems ; and I 
have therefore been obliged to place them in a separate list, as the number of radials in 
the cup is still an unknown quantity. 
