ECHINODERMATA. 55 



Locality and StratigrapMcal position. — This fragment was collected from the Marl- 

 stone near Ilminster; the specimen figured is all that has ever been found in that 

 locality ; the bed in which it was discovered is characterised by the presence of Ammonites 

 margaritatus, Montfort. It is interesting to find that M. Cotteau's specimen was col- 

 lected " dans les couches a Gryplima Cymhium de Vassy pres Avallon," where it is very 

 rare : this Gryphsea bed corresponds very nearly with the horizon of the Middle Lias in 

 Somersetshire, where the fragment before me was found. 



B. Species from the Great Oolite. , 

 Rabdocidaris maxima, Milnster. PL XII, fig. 6 ; PI. A, fig. 16. 



CiDAKiTES MAXiMUS. Goldfuss, Petrefact. Germanise, p, 16, t. 39, fig. 1 a, h. 



Knotted spine of Cidakis. Phillips, Geology of Yorkshire, t. 9, fig. 5. 



CiDARis MAXIMA. Morris, Catalogue of British Fossils, 2d edit., p. 74. 



Rabdocidaris maxima. Desor, Synopsis des Echinides Fossiles, p. 39. 



The large spine, figured by Professor Phillips, from the Grey Limestone (Great Oohte) 

 of Gristhorpe Bay, Yorkshire, (two of which I collected last summer,) I have identified 

 with a spine kindly sent me by Dr. Oppel, of Stuttgart, from the Inferior Oohte of Neufien, 

 Wiirttemberg, as typical of Miinster's species. A very large and fine specimen of this Great 

 Oolite spine is figured in PI. A, fig. 16 ; it measures five inches and a quarter in length. 

 The head is large ; the rim of the acetabulum is coarsely and deeply crenulated ; the neck 

 is short and smooth ; the stem is long and sub-fusiform, nearly five inches in length, it 

 gradually swells out in some specimens towards the middle, and tapers very little towards 

 the distal extremity ; the surface is covered with short, stout, thorn-like prickles, with 

 their points slightly directed forwards, which are irregularly developed, at considerable 

 distances apart; they do not form straight lines, but stud the surface in a somewhat 

 spiral order. 



None of the plates belonging to this large spine have yet been found in Yorkshire, 

 nor in the Great Oolite of the West of England. 



