PENTACEROS BULBIFERUS. 77 



1. PENTACEBOS BULBIFERUS, Forbes, sp. PI. XX, figs. 1, 1 a, 1 b, and 1 c; figs. 2, 2 a, 



and 2 6 ; PI. XXI, figs. 1, 1 a, I b, 3, 3 a, 

 4, 4 a ; PI. XXIII, figs. 2, 2 a. 



OBEASTER BULBIFEKTTS, Forbes, 1848. Mem. Geol. Surv. G-t. Brit., vol. ii, p. 468. 



Forbes, 1850. In Dixon's Geology and Fossils of the 



Tertiary and Cretaceous Formations of Sussex, 



pp. 328, 329, pi. xxiv, fig. 7. 

 Dujardin et Hupe, 1862. Hist. Nat. Zooph. fichin. (Suites 



ii Buffon), p. 389. 

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



edition, Jones), pp. 363, 370, pi. xxiv, fig. 7. 

 P. H. Carpenter, 1882. Geol. Mag., p. 12. 



Specific Characters. Disc and arms very convex. The centrale and primary 

 interradialia large and tuberculiform. The major radius approximately twice the 

 minor radius. Radialia of the arm conspicuous. Extremities of the arms swollen. 



Material. The specimens figured and described are all preserved in the 

 British Museum (Natural History). E. 5040 (PL XXI, fig. 1), 40175 (PI. XX, 

 fig. 1), 48748 (PI. XX, fig. 2), and E. 5041 (PI. XXI, fig. 3), which were bought 

 from J. Simmons, and 40399 (PI. XXI, fig. 4), from the collection of E. Charlesworth, 

 are all labelled as coming from the Upper Chalk of Bromley, Kent, which, 

 however, seems to be an inexact dealer's locality, probably intentionally mis- 

 leading. E. 5042 (PL XXIII, fig. 2), also bought of J. Simmons, is labelled 

 "Upper Chalk, Charlton, Kent." 



Other specimens are known in the Sedgwick Museum, Cambridge, Northamp- 

 ton Museum, and Brighton Museum. Specimens have also been described by 

 Valette from the South of France. 



This seems to be much the commonest as well as the most graceful of the 

 Chalk Pentacerotidae. 



Description. The general aspect of the plates of the disc gives this species a 

 very characteristic appearance, for the five primary interradialia and the centrale 

 are very prominent. They have a lobed widely-spreading base, and are swollen 

 on the upper surface into an almost spherical form. Their weathered surfaces 

 are pitted in a very regular manner, the pits indicating the former presence of 



