FROM THE LOWER GREENSAND. 295 



Isle of Wight, iu nodules from the Walpen and Ladder Sands and Clays, with 

 GryjAma sinuata and Ammonites {HopUtes) Martini, d'Orbigny, and in the bed with 

 GryphcBa at Shanklin Point, where several other Urchins, as Clypeopygus Fittoni, Wright 

 and EcUnospataguH Benevieri, Wright, have been found. The affinities of this species 

 are certainly with Cardiaster fossarius, the smaller forms of which it closely resembles in 

 many points of structure. The narrowness of the poriferous zones, common to both 

 forms, cannot afford a specific character ; therefore, until better examples are found for 

 comparison, I must regard the distinction between C. Benstedi and C. fossarius as 

 doubtful. 



Locality and Siratiyraphical Position.— Xwik^ Lower Greensand of Maidstone, and in 

 the Lower Greensand at Shanklin and Atherfield, Isle of Wight. 



Cardiaster latissimus, Ayassiz, 1840. PI. LXVII, figs. 1, 2 a — h. 



HoLASTER LATISSIMUS, Jffossis. Catalogus Syst, p. 2, 1840. 



— — Agassiz et Desor. Cat. Raisonu^, p. 133, 1847. 



— — d'Orbigny. Prodrome, t. ii, p. 177, 1847. 



— — d^Orbigny. Paleont. Frau^aise, Ter. Cret., torn, vi, 



p. 92, pi. 837 and 838, 1853. 

 Cardiaster suborbicularis, Forbes. Mem. Geo!. Surv., decade iv, pi. ix, notes, 1852. 



— — Morris. Catal. Brit. Foss., p. 73, 1854. 



Diagnosis. — Test cordiform, broader than long, much depressed; anterior border 

 very wide, deeply grooved by the anteal sulcus, sides expanded ; posterior half contracted 

 and becoming rapidly narrow behind, upper surface slightly convex ; anterior half more 

 rotund and elevated than the posterior half, which devclopes a ridge between the disc and 

 the posterior border, this region is narrow, elevated, and obliquely truncated, having the 

 vent high up near the dorsal surface. Ambulacral pores narrow, poriferous slightly 

 unequal. Anteal sulcus deep, ambulacrum with very minute round pores. Base slightly 

 convex, depressed near the mouth, convex and elevated in the middle and posterior 

 region over the plastron. 



Dimensions. — Large specimen, fig. 1. Antero-posterior diameter two inches and 

 -i%ths; transverse diameter two inches and iijths ; height y^ths of an inch. 



Small specimen, fig. 2. Antero-posterior diameter two inches and i^ths; transverse 

 diameter two inches and -i%ths ; height anteriorly -j^ths of an inch, posteriorly i^ths of 

 an inch. 



Description. — This beautiful Cardiaster is entered in our catalogues of British 

 Urchins as C. suborbicularis. It appears, however, to be identical with Holaster 



