16 FOSSIL ASTEROIDEA.. 



Body of medium size. Disk moderately large. Rays well produced, rather 

 broad at the base aud tapering to the extremity. General form depressed and 

 thin. Marginal contour stellato-pentagonal, the major radius measuring more 

 than twice and a half the minor radius. Marginal plates broad, the supero- 

 marginal series of the two sides of the ray meeting in the median radial line. 

 Interbrachial arcs deeply indented and well rounded. Margin rather thin. 



The infero-marginal plates are more than fifteen in number, counting from the 

 interradial line to the extremity. They form a broad conspicuous border to the 

 actinal area, which is relatively broad in proportion to the size of the disk. The 

 largest infero-marginal plates near the median interradial line measure about 

 5'5 mm. in breadth, and about 2'5 to 2'75 mm. in length. The breadth decreases 

 slightly from this point as the plates approach the base of the ray, and then 

 much more rapidly, the plates on the outer part of the ray having the length 

 considerably in excess of the breadth. The plates are tumid and roundly 

 bevelled at the lateral edges, but are flatly rounded at the margin of the disk, and 

 without tumidity there. The whole superficies of the plate is covered with large, 

 rather deeply depressed, hexagonal punctations, closely placed, which give 

 somewhat of a honeycomb appearance to the plate (see PL VIII, fig. 1 b). These 

 are the marks left by the granules previously borne upon the plate. Upon a 

 number of the plates in the example figured on PI. VIII, fig. 1 a, the granules are 

 still preserved in situ. They are large and closely placed. The punctations, 

 and consequently the granules, in this species are coarser than in any of the other 

 Cretaceous forms known to me. I have not been able to assure myself of the 

 presence in this example of any pedicellarise on the infero-marginal plates. 



The adambulacral plates are broader than long, except on the outer part of the 

 ray, and their armature appears to have consisted of five or six regular series of 

 spinelets. This is indicated by the presence upon the surface of the plate of that 

 number of ridges, running parallel or subparallel to the ambulacral furrow, each 

 having four or five articulatory elevations and intervening pits upon which 

 spinelets had previously been borne. The spinelets were probably short, and 

 similar to those described in GaUiderma Smithise and Galliderma mosaicum, but I 

 have not found any preserved in specimens which I consider to be undoubted 

 examples of Nymphaster Goombii. 



Dimensions. — In the type specimen, figured on PI. VIII, fig. 1 a, the major 

 radius is more than 56 mm., and the minor radius 23 mm. The breadth of the ray 

 between the fourth and fifth infero-marginal plates measures about 15 mm. 



Locality and Stratigrapkical Position. — The specimen figured is from the Lower 

 Chalk of Balcombe Pit, Amberley. The species has also been obtained from the 



