124 



ECHINOTHURIA 



vertical filament form latijjora, Ag., and depressed examples with the median impres- 

 sion almost absent are E. depressa, Ag. A carefnl study of the original types has, how- 

 ever, convinced my learned friend that they are all varieties of one form, and not distinct 

 species. 



Localiiy and StraUgrajjhkal Fositioti. — This species is found very rarely in the hard 

 beds of the Lower Chalk near Lewes, in Sussex, and in the Grey Chalk near Folkestone. 

 From this stratum my best specimen was collected by Captain Cockburn, R.A., to whose 

 kindness and liberality I am indebted for the example. 



The Foreign Localities given by M. Cotteau are Villers-sur-Mer, Bruneval, Saint- 

 Jouin, Vaches-Noires, Dives (Calvados); Fecamp, le Havre, Rouen (Seine-Inferieure) : 

 Gace, La Perriere (Orne) ; Nogent-le-Bernard (Sarthe) ; Saint-Fargeau (Yonne) ; la 

 Bedoule, Cassis (Bouches-du-Rhone). In all these localities it is very rare, and occurs 

 in the Etage Cenomanien, in the zone of Scaphites cequalis, which is the equivalent of the 

 English Lower Grey Chalk. 



Hidory. — This species was found in the Lower Chalk of Essen and Gehrden, West- 

 })halia, and was first figured and described by Goldfuss in his ' Petrefacta Germanise.' 

 Since that time it has passed through a series of changes which are most correctly read 

 in the long list of synonyms introductory to this article, and to which I commend the 

 reader's especial attention. 



Genus — Echinothuria,^ Woodioard, 1863. 



" Test globular ?, diameter of compressed specimen four inches, thickness half an inch, 

 lantern projecting half an inch ; com[)osed of ten segments or double series of imbricating 

 plates, ornamented with obscure miliary granules and small spine-bearing tubercles, a few 

 larger than the rest ; inter -amhulacral plates narrow, slightly curved, with the convex edge 

 upwards and overlapping ; the alternate plates bearing one lai-ge extero-lateral tubercle, 

 perforated, and surrounded by a raised ring and smooth areola ; largest plates measuring 

 six lines in length, the smallest three lines or less (the longest in second specimen equal- 

 ling seven lines) ; ambtdacral plates seven lines long, equalling the breadth of the exposed 

 portion of eight plates, similar to the former, but curving and imbricating downwards 

 towards the dental orifice, and having two small plates, each perforated by a pair of pores, 

 intercalated in a notch of the middle of the lower margin ; a third pair of pores perfo- 

 rating the plate itself a little external to the centre ; primary tubercles few, irregularly 

 distributed. 



1 " Etymologists need not trouble themselves about the derivation of this name ; it is intended merely to 

 express the dilemma in the writer's mind, arising from imperfect knowledge, butwiiich he believes to have 

 no foundaiion in nature." — ' Geologist,' vol. vi, p. 330. 



