ECHINODERMATA. 



29 



Wright, and Cidarites maximus, Miinster, but it presents many important characters by 

 which it is distinguished from both. From Cidaris Foioleri it differs in wanting the 

 regular close-set row of marginal granules, with the four internal rows of minute granules 

 in the ambulacral areas, which form so fine a character in that Inferior Oolite species 

 (PI. I, fig. 4 e) ; the irregular distribution of the small tubercles in these areas in Cidaris 

 Edwardsii forms a marked distinction between them : the poriferous zones are occupied 

 by large pores, separated from each other by thin septa ; in Cidaris Fowleri the pores are 

 small, oblong, and separated by a thick portion of the test (fig. 4^). The tubercular 

 plates in Cidaris Edwardsii being narrow, there are consequently a greater number of 

 primary tubercles in the inter-ambulacral areas : the areolas, likewise, are oblong, and 

 always confluent in the vertical direction ; whereas in Cidaris Foioleri the areolas are 

 nearly circular (fig. 4 e), and each is surrounded by a circle of granules. The inter- 

 tubercular space or miliary zone in Cidaris Fdwardsii is filled with small perforated 

 tubercles, but in Cidaris Fowleri the same space is occupied by small imperforate granules, 

 more numerous, but less regular in size and distribution (fig. 4 e) : the spines in Cidaris 

 Fowleri are stout, and have well-developed rows of forward-directed prickles (fig. 4 d) ; 

 whereas in Cidaris Edioardsii they are long and slender, with small irregular elevations of 

 the surface, which is hkewise sculptured with microscopic longitudinal lines. 



Locality and Stratigrapliical position. — This fine urchin was discovered in the upper 

 shales of the Lower Lias, or Middle Lias, by G. E. Gavey, Esq., C.E., at Mickleton tunnel, 

 near Chipping Campdeu, in the zone of that formation containing Ammonites maculatus, 

 Young and Bird. The bed which yielded Cidaris Edwardsii contained likewise other 

 species of Echinoderms in a fi.ne state of preservation : these were — 



Cidaris Edwardsii, Wright 

 Hemipedina Bowerbankii, Wright, 



plates of 

 TJraster Gaveyi, Forbes 



Tropidaster pectinatus, Forbes 

 Ophioderma Gaveyi, Wright 

 Extracrinus rohustus, Wright 



„ Two species undetermined. 



Besides these Echinodermata, 40 species of Conchifera, 8 species of Gasteropoda, and 

 10 species of Cephalopoda, with Serpulse, and 3 new species oi Pollicipes, were associated 

 with the same. For more details, the reader may consult Mr. Gavey's paper.* Isolated 

 plates of Cidaris Edioardsii have been collected from the same zone of the Lias in other 

 localities in Gloucestershire, but the specimen we have figured is the only one which 

 displays the true character of the species. Professor Morris has kindly communicated a 

 Cidaris with spines, collected from the Lias at Lyme Regis, which has proved to be a small 

 specimen of Cidaris Edwardsii : this beautiful fossil shows many of the long slender 



* ( 



Quarterly Journal of the Geological Society,' vol. ix, p. 29. 



