FROM THE KIMMERIDGE CLAY. 167 



the ambulacral areas are moderately wide, they have two rows of regular, promment, mar- 

 ginal tubercles, which gradually diminish in size from the base to the summit of the areas, 

 and are separated by a zig-zag line of small granules occupying the line of the suture 

 (fig. 2 b) ; the poriferous zones are slightly waved, the pores are separated by thick septa, 

 the external surface of which form slight eminences, and there are five pairs of pores 

 opposite each large plate. 



The inter-ambulacral areas are three times the width of the ambulacral, each plate sup- 

 ports two primary equal-sized tubercles (fig. 2 b), which have prominent bosses with well- 

 defined areolas, surrounded by incomplete circlets of small granules (fig. 2 b). 



The long, round, slender spines referred to this species (fig. 2 c) have their 

 surface sculptured with fine longitudinal lines ; the articulation is small, with a smooth 

 rim ; the head is short and stout, with a thin, finely milled, prominent ring ; the stem is 

 much smaller in diameter than the head. 



Affinities and differences. — The fragment (fig. 2 a) is all that I have seen of the test 

 of this species ; it belongs to the section with several rows of tubercles in the inter- 

 ambulacra, but the specimen is too imperfect for comparison with other forms. 



Locality and Stratigrapliical position. — This species was collected by Z. Hunt, Esq., 

 from the Kimmeridge Clay, at Hartwell, Bucks, and was kindly communicated by Professor 

 Morris, to whose collection it belongs. 



Hemipedina Cunningtoni, Wriglit. PI. XH, fig. 3 a, b. 



Hemipedina Cunningtoni. "Wright, Annals and Magazine of Natural History, 2d series, 



vol. xvi, p. 198. 

 — — Woodward, Memoirs of the Geological Survey, Decade v, 



" Notes on Echinopsis." 



Form unknown ; ambulacral areas with two marginal rows of very small tubercles ; 

 poriferous zones straight, pores obliquely disposed ; inter-ambulacral areas with two rows 

 of tubercles on the zonal sides of the plates, miliary zone wide, filled with from eight to 

 ten rows of small granules ; bosses large and prominent ; areolas surrounded by complete 

 circles of granules. 



Dimensions. — Transverse diameter, upwards of one inch ; height unknown. 



Description. — The fragment figured 3 a, b, is all that is known of this urchin, which 

 shows that it belongs to that group of the Hemipedinas having two rows of tubercles on 

 the poriferous side of the plates, and a wide miliary zone between them. It is much to be 



