340 THE VOYAGE OF H.M.S. CHALLENGER. 
fourth radial is sometimes a syzygy. The rays generally divide four and sometimes five 
times ; and their subdivisions are equal in value or nearly so. The first joint after each 
axillary bears a pinnule, and the third is usually a syzygy. 
The terminal parts of the arms have a large number of undeveloped pinnules. Those 
on the lowest parts of the rays have large, thick joints, the basal ones cuboidal and the 
rest oblong. Those borne by the radials and lower distichals receive their ambulacra 
direct from the peristome, or from the primary ambulacra of the disk. 
Remarks.—The name Metacrinus for this very well characterised genus originated 
with Sir Wyville Thomson ; but he drew up no diagnosis of it. Indeed it was only by 
finding the name in his handwriting upon a proof of Pl. XLVIL. that I was informed of his 
recognition of the type as distinct from Pentacrinus, under which name it had been 
mentioned in the Station Book, and in various publications that dealt with the work of 
the Challenger in the Pacific. I had known of the existence of a second living genus 
of Pentacrinidse for some months before the Challenger and “Blake” Crinoids came into 
my hands. For my friend Mr. Charles Stewart, F.L.S., the present Curator of the 
Hunterian Museum at the Royal College of Surgeons, had shown me early in 1881 a very 
fine dry specimen which had been obtained in the neighbourhood of Singapore by one of 
the ships belonging to the Eastern Telegraph Company. It was accompanied by a stem- 
fragment of another species which I now know to belong to the same genus. Thanks to 
his kindness, I have been able to describe them recently,’ together with yet another 
species which had been dredged in the Japanese Seas by Dr. Déderlein, the Conservator 
of the Natural History Museum at Strassburg, who courteously placed it in my hands for 
this purpose. Eleven species were dredged by the Challenger, and there is another 
which I have not examined personally. It was dredged by the famous “ Vega” in 
Yeddo Bay, during her stay in Japan in October 1879; but no description of it has 
yet been published. It is at present im the hands of Prof. 8, Lovén of Stockholm ; 
and with his characteristic kindness he not only sent me some fragments of the stem, 
but also allowed Mr. Percy Sladen, who was examining the Starfish collection in the 
Stockholm Museum, to draw up a description of it for me. So carefully was this done, 
that I have been enabled to recognise the affinities of the type, and to assign it a 
place in the classification of the genus which appears on p. 344. 
Both the calyx and the stem of Metacrinus, but especially the former, present very 
striking differences from the corresponding parts in Pentacrinus. In the latter genus 
it is quite the exception for the number of radials to exceed three, which is so constant in 
Apiocrinus, Millericrinus, Encrinus, and Comatula; and even when there are more, 
none of them bear any pinnules. ‘Thus there is no pinnule on the third joint of the 
abnormal ray of Pentacrinus miilleri represented on Pl. XV. fig. 2, in which the axillary 
is the fourth joint above the basals ; nor on any of the five joints below the radial axillary 
1 On Three New Species of Metacrinus, Trans. Linn. Soc. Lond. (Zool.), ser. 2, vol. ii. pp. 435-447, pls. 1.-lii. 
