FROM THE GREY CHALK. lliJ 



EcHiNOCYnius MESPiLiA, Woodward. PI. XXH, figs. 3 a, h, c, d. 



Cyphosoma MESPILIA, Woodward. App. DecaJe V, Mem. of the Geol. Survey, 

 p. 3, 1856. 



Test small, circular, inflated or depressed, convex above and below, with subequal 

 apertures ; poriferous zones straight, simple, pairs of pores very oblique ; tubercles nearly 

 equal, j)rominent, imperforate and crenulated ; areolae small, radiated, with elongated 

 miliary granules, sutural impressions slight ; inter-ambulacra wide, with two rows of 

 tubercles, seven to eight in each ; ambulacra narrow, with seven to eight tubercles, alter- 

 nate, and irregular. 



Dimensions. — Height three lines ; transverse diameter five lines. 



Description. — This species was discovered by my late friend, Dr. S. P. Woodward, 

 who found it in the Lower Hard White Chalk along with Cyphosoma simplex, Forb., and 

 Salenia granulosa, Forb. It is a pretty little Urchin, with inflated sides ; the test is nearly 

 convex above and below, the poriferous zones are straight and simple, the unigeminal 

 pores are very oblique, the ambulacral areas are narrow, and the tubercles, seven or eight 

 in number, are alternate and irregular (fig. 3), one of the rows being partially abortive. 

 The inter-ambulacral areas are wide, and have two rows of prominent tnbercles, seven to 

 eight in each row (fig. 3), which occupy the centre of the plates, and are surrounded by 

 small radiated areolae, formed by an oblique arrangement of the elongated granules 

 thereon, and imparting an ornamented character to the test. The mouth-opening is more 

 than one third of the diameter of the test, the peristome is nearly equally lobed, and the 

 incisions are wide and deep. The discal opening is larger than the oral in diameter. 



Affinities and Differences. — This Urchin very much resembes E. dijficUis ; it lias, 

 however, a more inflated test, with stronger radii on the areolae, and larger oral and discal 

 apertures. Its author considered it " a very distinct species," and called my especial 

 attention to it. A careful comparison of the accurate figures of both species drawn on 

 PI. XXII will enable the student to appreciate the affinities and differences between tiiem 

 better than any description, however elaborate. 



Locality and Sfratiyraphical Position. — E. mespilia has been collected only from the 

 Lower Chalk, in the hard beds of which it has been found, associated with Cyphosoma 

 simplex and Salenia granulosa. The only specimens I have seen arc in the British 

 Museum. 



