OPHIODERMA. 143 



Locality and Stratigraplncal Position. — OpModerm.a Milleri, Phil., is found in the 

 same stratigraphical horizon in Yorkshire as OpJdoderma Gaveyi occupies in the Middle 

 Lias of Gloucestershire. The presence of Ammonites capricornus, Schloth. {Am. macidatus. 

 Young and Bird), and Avicula incequivalvis. Sow., in the rock containing the large 

 specimen belonging to the museum of the Yorkshire Philosophical Society (PI. XVI, 

 fig. 4), determines the zone of life to which this Ophiura belongs. It is found in bands 

 of shelly calcareous sandstone belonging to the main Ironstone series or lower portion 

 of the Marlstone beds at Staithes, near Whitby, on the Yorkshire coast, with Cardium 

 truncatum, Phil., Avicida incequivalvis, Sow., Modiola scalprum, Sow., Lima Ilermanni, 

 Voltz, and Pholadomya amhigiia, Sow. (See p. 142.) 



The foregoing section, by Mr. L. Hunton,^ of the Marlstone at Rockcliff, near Whitby, 

 Easington Heights, Mudges Survey, clearly defines the position of the Ophiura-beds in 

 Yorkshire. 



History. — This Sea-star was first rudely drawn by Young and Bird, 1822, in their 

 'Geological Survey of the Yorkshire Coast.' 1829, Professor John Phillips named the 

 species, and gave a good figure of it in his ' Geology of Yorkshire,' but did not 

 describe it. 1836, M. Agassiz, in his 'Prodrome d'une Monographie des Radiares 

 ou Echinodermes,' p. 193, proposed for this and other fossil species the genus Ophiu- 

 rella, without defining the characters on which it was based. 1850, M. A. d'Orbigny, in 

 his ' Prodrome de Paleontologie,' t. i, p. 240, proposed the genus Palaocoma, giving 

 P. Milleri as the type of the same ; this genus he thus described : — " Ophiures a quatre 

 rangees de pieces aux bras, sans petites pieces intermediares." 1852, in my ' Con- 

 tributions to the Palaeontology of Gloucestershire,' p. 42, I referred this species to 

 Miiller and Troschel's genus Ophioderma, associating it with other congeneric forms from 

 the Middle Lias, as 0. Gaveyi, 0. Eyertoni, 0. temiibrachiata. In 1854, Professor E, 

 Eorbes, in his additions to Morris's Catalogue of British Eossils, and 1857, M. Pictet, in 

 his ' Traite de Paleontologie,' t, iv, p. 274, referred this species to the genus Ophioderma. 

 1862, Dujardin and Hupe, in their ' Histoire naturelle des Echinodermes,' adopted the 

 genus PalcBocoma, and recorded the species as Palceocoma Milleri. 



Ophioderma Egertoni, Broderip, sp. PL XV, fig. 4, a, h ; fig. 5. 



Ophiura Egertoni, Broderip. Trans. Geol. Soc, 2 series, vol. v, pi. xii, figs. 



5, 6, 6*, 1835. 

 _ _ Forbes. Proceed. Geol. Soc, vol. iv, p. 233, fig. 4, 1843. 



Ophiodekma Egertoni, Forbes. Morris, Cat. Brit. Fossils, 2nd ed., p. 84, 1854. 



— — Oppel. Die Juraformation, p. 267, 1856. 



— _ Wright. Brit. Association Report for 1856, p. 403, 1857. 



— — Pictet. Traite de Paleontologie, tome iv, p. 274, 1857- 



— — Dujardin et Hupe, Hist. Nat. des Echinod., p. 234, 1862. 



1 ' Trans, of the Geol. Soc. London,' p. 215, vol. v, second series, 1836. 



