222 THE VOYAGE OF H.M.S. CHALLENGER. 
which he provisionally named Hyocrinus bethellianus? with the following remarks :— 
“The last is a beautiful little thing which we dredged from a depth of 2325 fathoms at 
Station 223, in lat. 5° 31’ N., long. 145° 13’ E., in the east Pacific, with a bottom of 
Globigerina ooze, and a bottom-temperature of 1°°2C. It certainly is in many respects 
very unlike the adult Hyocrinus bethellianus ; but it may possibly turn out to be the 
young of that species. There was only one specimen.”* No reference whatever was 
made to this type in the description of Hyocrinus which was subsequently published in 
The Atlantic, and is substantially the same as that which appeared in the Journal of the 
Linnean Society. One would be inclined to conclude from this that the specimen in 
question was not a young Hyocrinus after all; for even though it was obtained in the 
Pacifie, reference would probably have been made to it in Sir Wyville’s later account of 
this very interesting genus. But as the specimen has totally disappeared, and has eluded 
all Mr. Murray’s anxious search, I am naturally unable to say anything about it. 
B. On tue Systematic Position or Hyocrinus. 
Hyocrinus was established by Sir Wyville Thomson in the year 1876,’ with the 
remark that “it presents certain general resemblances and even certain correspondences 
in structure which seem to associate it also with Rhizocrinus. There seems little doubt 
that Rhizocrinus finds its nearest known ally in the Chalk and Tertiary Bourgueticrinus, 
and that it must be referred to the neighbourhood of the Apiocrinide. Were it not that 
Bathycrinus and Hyocrinus are so evidently related to Rhizocrinus, the characters of the 
Apiocrinidee are so obscure in the two first-named genera that one would certainly have 
scarcely been inclined to associate them with that group.” Bathycrinus, though an 
aberrant form, is far more closely related to Rhizocrinus than Hyocrinus is. It has the 
same form of stem-joint and the same absence of pinnules from the arm-bases ; while the 
arm-joints themselves are united in pairs in a very nearly similar manner in both genera. 
But except in this last point, there is no resemblance between Rhizocrinus and Hyocrinus. 
The only known species of the latter genus was said by Sir Wyville Thomson to have 
“much the appearance, and in some prominent particulars it seems to have very much 
the structure, of the Palzozoic genus Platycrinus, or its subgenus Dichocrinus.”* In 
fact, Sir Wyville seems to have had considerable hesitation in referring Hyocrinus to the 
Apiocrinide ; and it was eventually associated by Zittel along with Plicatocrinus, in a 
family Plicatocrinide. But the definition which he gave of the family was far from bemg 
a satisfactory one, as it stated that basals were absent, which is by no means the case in 
Hyocrinus, and also that there are long, forked arms. Since then, however, he has found 
that there is an axillary second radial (first brachial, Zittel) in Plicatocrinus, which thus 
1 Journ. Linn. Soc. Lond. (Zool.), vol. xiii. p. 55. 2 Tbid., p. 48. 3 Ibid., p. 51. 
’) =. 
"eee 
