1030 DR. J, W. GREGORY ON THE CLASsification ([Dec.15 
those of Asterids and of the Hchinid Paleodiscus. As the two 
elements which have fused to form the vertebral ossicles of later 
Ophiurids are unattached in the members of this order, I propose 
for it the name Lysophiure’. 
No one has worked at the Paleozoic Ophiurids without being 
impressed by the unsatisfactory nature of many of the genera. 
In my earliest paleontological paper (1889) I pointed out that 
Protaster would have to be split up into more than two genera 
[5. p.27]. Stiirtz, both in 1890 [16. p. 245] and 1893 [17. p. 19], 
also insisted that Protaster includes a miscellaneous group of 
species, and that the Protasters of Forbes, Billings, Hall, and 
myself are distinct. I shrank from the task of dismembering this 
genus in 1889, as I hoped for better specimens of the type species. 
None such, however, have been forthcoming. As I am now 
bound to attempt to indicate the relations of the fossil and recent 
forms in an account of the Ophiuroidea for Prof. Lankester’s 
‘Oxford Natural History,’ I delay no longer. In order to 
simplify my task in that place, I offer the following synopsis of 
the classification of the Paleozoic Ophiurids, with diagnoses of 
some of the genera. 
Order I. LYSOPHIURZ. 
Diagnosis.—Ophiuroidea of which the ambulacral ossicles are 
alternate and are not united into vertebral ossicles. There are no 
ventral arm-plates, and the underside of the arm is occupied by an 
ambulacral furrow. 
Remarks.—This order includes a group of Paleozoic Ophiurids 
in which the arm-structure is on the same plan as in the Asterids ; 
for there are no ventral arm-plates, there is an ambulacral groove, 
and the ambulacral plates are in double series. The members of 
the order differ from the Asterids by having the arms sharply 
marked off from the disc; while the alimentary canal was, in all 
probability, entirely limited to the disc. 
So far as is known at present, the order was limited to the 
Paleozoic period; but it is necessary to consider whether a few 
recent forms ought not to enter it. In Ophiohelus and Ophiothohia 
the ambulacral plates occur as pairs of rod-like plates, instead of 
as vertebral ossicles. They therefore, in this respect, resemble 
Lysophiurids. On application to the Zoological Department of 
the British Museum, I find that both genera are represented only 
by the small single specimens dredged by the ‘Challenger.’ It is 
too great a responsibility to subject these fragile type specimens 
to the risk of re-examination, especially as the nature of the 
articular surfaces could not be determined without dissection. 
Both specimens are so small, that, as Prof. Bell suggests, it is quite 
possible they are not mature. 
The members of the two genera, however, differ from the 
Paleozoic Lysophiure in three respects: they have the ambulacral 
1 From Avors, dissolution, unattachment. 
