102 FOSSIL ASTBROIDBA. 



becoming smaller and shorter towards the distal oral region, where they are 

 almost hidden by the scales of the mouth-tentacles. Arm-spines smooth and 

 short, seldom longer than an arm-segment. Tentacle-scales numerous. The 

 innermost pair of tentacle-pores narrow, surrounded by numerous tentacle-scales, 

 and opening obliquely into the oral slits. In the back of the disc, where the arm 

 joins it, a notch usually edged with papillas. Two genital slits arise from the 

 sides of the mouth-shields. 



The following species are placed provisionally in this genus, to which the 

 known characters would approximate them. The evidence, however, in every 

 case is incomplete. 



1. OPHIURA SERBATA, Roemer. PI. XXVII, figs. 3, 3 a, 3 b, 3 c, 3 d, 3 e. 



OPHIURA SEERATA, 'Roemer, F. A., 1841. Die Versteiuerungen norddeutsch. 



Kreidegeb., p. 28, pi. vi, fig. 23. 

 Forbes, 1843. Proc. Geol. Soc., vol. iv, p. 234, fig. 2. 

 Reuse, 1845-6. Die Verstein. bohm. Kreide-form., vol. ii, p. 



58, pi. xx, fig. 26. 

 Forbes, 1850. lu Dixou's Geology and Fossils of the Tertiary 



and Cretaceous Formations of Sussex, p. 337, pi. xxiii, 



figs. 2, 3, 3 a, 3 b. 



Morris, 1854. Cat. Brit. Foss., ed. 2, p. 84. 

 Forbes, 1878. In Dixon's Geology of Sussex (new edition, 



Jones), p. 369, pi. xxiii, figs. 2, 3, 3 a, 3 b. 



Specific Characters. Conspicuous pear-shaped radials. Remainder of dorsal 

 surface of disc covered with scales. Upper arm-plates occupying great propor- 

 tionate width of arm. Six, occasionally seven ?, spines on each side of arm-segment. 



Material. Only two fragments of arms were originally available for descrip- 

 tion by Roemer. The specimens described by Forbes were more nearly complete, 

 one specimen showing a considerable portion of the disc and the proximal portion 

 of four arms (figured on PL XXVII of this Monograph), now in the British 

 Museum (Nat. Hist.), and bearing the registered number E. 5043 (Dixon Coll.). 

 There are fragments of arms in several collections which can apparently be 

 ascribed to this species. 



Description. The disc is 15 mm. in diameter. Almost the whole of the dorsal 

 covering has disappeared in the specimen figured, thus exposing the inner surface 

 of the mouth-plates. The jaws (oral angle plates) are clearly seen. They are 

 long and slender and do not meet inter-radially. The grooves for the water 



