148 



LIASSIC OPHIURIDiE. 



are well developed and much elongated transversely ; their position and character is well 

 seen in PI. XV, fig. 1, a,b, c. 



The buccal plates are absent, but the ten osselets by which the rays were articulated 

 with the disk are well preserved in the specimen figured in PI. XVII, fig. 1, a. These 

 form a considerable star-shaped oral aperture, from the angles of which a tooth-like 

 process projects inwards towards the mouth. 



Affinities and Differences. — This Ophiura in its general contour resembles OpJiioderma 

 Milleri ; it is distinguished from that species by having a larger disk, with more slender, 

 tapering rays ; the arm-plates are likewise much smaller, and the radial plates of the 

 disk larger. The magnitude of the disk, the structure of the radial plates, and the size 

 of the rays, distinguish it from Ophioderma Egertoni. 



Locality and Stratigraphical Position. — This Sea-star was discovered by my friend 

 Mr. Gavey, P.G.S., in the Middle Lias of Mickleton Tunnel, near Chipping Campden, 

 Gloucestershire, whilst making the West Midland Railway ; it came from the zone of 

 Ammonites capricornus ; with that Ammonite were associated Cidaris Edwardsii, Wr., 

 Hemipedina Bowerbankii, Wr., Uraster Gaveyi, Porb., Tropidaster pectinatus, Porb., and 

 Pentacrinus rohustus, Wr, Besides these Radiata about sixty species of Mollusca 

 were discovered in the same bed. 



I must refer to Mr. Gavey 's memoir and section of the cuttings for further details.^ 

 Fragments of the rays have been found at Hewletts Hill, near Cheltenham, in the same 

 zone of the Middle Lias. 



History. — Pirst figured and described in the ' Annals and Magazine of Natural History' 

 for 1852, from specimens kindly sent me by Mr. Gavey. I am not aware that it has been 

 found in any other localities. 



Ophioderma carinata, Wright, n. sp. PI. XVI, fig. 1, a, b. 



Disk small, flat, pentagonal ; radial plates small, the pairs closely approximated, and 

 separated from the adjoining radial plates by a smooth membranous space ; arms long, 

 slender, and gradually tapering ; dorsal plates narrow, with an elevated central carina ; 

 membranous covering of the disk smooth, and extending like a web between the base 

 of the rays. 



Dimensions. — Diameter of the disk seven tenths of an inch; length of the rays, three 

 inches, or about four and a half times the disk's diameter ; breadth of the ray at its base 

 one fifth of an inch. 



1 " Railway Cuttings at Mickleton Tunnel and Aston Magna," by G. E. Gavey, Esq., F.G.S. ; ' Quart. 

 Journ. Geol. Soc.,' vol. ix, p. 29, 1853. 



