692 PROF. W. J. SOLLAS ON SiLrKIAN [NoV. 1 899, 



37. Fossils in the University Museum, Oxford : I. On Silurian 

 EoHiNoiDEA and Ophiuroidea. By Prof. W. J. Sollas, M.A., 

 D.Sc, LL.D., F.R.S., F.G.S. (Eead April 12tli, 1899.) 



As the work of arranging the Geological Collections of the Oxford 

 University Museum proceeds, much interesting material is brought to 

 light. Some of this will be described from time to time ; but as the 

 descriptions will be undertaken by more than one observer, some 

 advantage may be gained, if only in indicating the common source 

 of the material, by bringing these contributions together under the 

 title of ' Fossils in the University Museum, Oxford.' In this com- 

 munication I propose to treat of some Silurian Echinoidea and 

 Ophiuriodea. 



The Family Eucladidse. 



The interesting and remarkable fossil described by Dr. Woodward 

 under the name of Eucladia Johnsoni has recently been placed by 

 Dr. Gregory in a new family — the Eucladidse, of which hitherto it 

 has been the sole representative. We are now able to assign it 

 companions, and to add to our knowledge of its structure, with the 

 result, as I believe, of showing that a more fundamental distinction 

 exists between this group and all other Ophiuroidea than between the 

 two recognized subdivisions Ophiurae and Euryalse. The family 

 must be relegated at least to a new order, which 

 may be called the Ophiocistia.^ 



Before proceeding further, it will be necessary to clear up certain 

 doubtful points in the anatomy of Eucladia Johnsoni. The exposed 

 surface of the fossil was described by Dr. Woodward^ as the ventral 

 aspect, and good reasons were given for this proceeding, attention 

 being called to the fact that the arms originate from it, and that 

 it bears the madreporite. The existence of vertebral ossicles is 

 not asserted. A re-examination of the fossil led my friend, 

 Dr. Gregory, to ascribe a dorsal character to its exposed surface ; 

 and a curious pentagonal rosette in the centre, rightly interpreted 

 by Dr. Woodward as the buccal armature, came consequently to 

 be regarded, though with expressed doubt, as ' radial plates.' 

 A dorsal position of the madreporite necessarily followed, and, 

 indeed, was claimed as an archaic character.^ Certain markings 

 associated with the fossil were described and figured by Dr. Gregory * 

 as vertebral ossicles. 



The study of the new material which has come under my obser- 

 vation, as well as of Eucladia Johnsoni itself, leads to the conclusion 

 that Dr. Woodward was certainly correct in his determination of 

 the aspect of his specimen and that the pentagonal rosette is the 

 buccal armature, for it is interradial in orientation, and closely 

 ]-esembles structures obviously of that nature in the new Eucladid- 

 forms to be presently described ; the ventral position of the madre- 



^ IC10TJ7, a box, Lat. cida. '^ Geol. Mag. 1869, p. 241. 



3 Proc. Zool. Soc. 1896, p. 1040. * Ibid, p. 1041, fig. 6. 



