330 



THE GEOLOGIST. 



geological record," as it seems to indicate the former existence of a family 

 or tribe of creatures whose full history must ever remain unknown, 

 Order JEchinidce. Genus Eehinothuria.* 



JE. jioris, n. sp. ; test globular ?, diameter of compressed specimen 4 

 inches, thickness \ an inch, lantern projecting \ an inch ; composed often 

 segments or double series of imbricating plates, ornamented with obscure 

 miliary granules and small spine-bearing tubercles, a few larger than the 

 rest; interambulacral plates narrow, slightly curved, with the convex 

 edge upwards and overlapping; the alternate plates bearing one large 

 extero-lateral tubercle, perforated, and surrounded by a raised ring and 

 smooth areola ; largest plates measuring 6 lines in length, the smallest 3 

 lines or less (the longest in second specimen equalling 7 lines) ; amhula- 

 cral plates 7 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 perforating the plate itself a little external to the 

 centre ; primary tubercles few, irregularly distributed. 



Spines of three kinds ; those adhering to the plates minute and striated ; 

 fragments of larger spines (not certainly belonging to the species), striated, 

 annulated, and furnished with a prominent collar to the articular end (Fig. 

 C) ; the third kind minute, clavate and truncate, articulated (?) to a slender 

 stalk (Fig. E d). 



Explanation or Plate. 



Fig. A. Mr. Flower's fossil; a, centre of upper surface; b, an interambulacral seg- 

 ment ; c, ambulacrum ; d, lateral half of a second interambulacrum. 



Fig. B. Mr. Glass's specimen; o, dental apparatus ; a, inner surface of apical portion 

 of an ambulacrum; c, e, g, ?, I, position of the live arabulacral segments; b, d,f, h, k, 

 position of five interambulacral segments, of which only fragments remain ; d, k, posi- 

 tion of small clavate spines. 



Fig. C. Three ambulacral plates near the summit, showing to what extent their outer 

 ends are overlapped by the interambulacral plates. 



Fig. D. One of the larger spine-fragments, natural size and magnified. 



Fig. E. Oral disk and teeth of a recent Cidaris; a, the five ambulacral segments with 

 notched and perforated plates. 



COEEESPONDENCE. 



Foraminifera oftlie Chalk. 



Sir, — I was much pleased, in looking over your " Thoughts on Dover 

 Cliffs," b} r meeting with the Foraminifera figured in Plate I. representing 

 so many forms ; also with the notes of the figured specimens b} r Professor 



* 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, but which he believes to have uo foundation in nature. 



