124 CRETACEOUS LAMELLIBRANCHIA. 
Distribution : 
(i) Lower Chalk: Fulbourn Asylum. Zone of H. subglobosus of Shelford, 
Cherry Hinton, and cutting east of South Cave Station. 
(ii) Middle Chalk: Lewes. Melbourn Rock near Hitchin. Zone of fh. Cuvieri 
of Dover. Zone of Terebratulina gracilis of Dowlands (near Rousdon), the 
Dorset coast, Dover, the Sussex coast, Whyteleaf (Warlingham), St. Giles’ Hill 
(Winchester), Hitchin, Worsted Lodge, and Mutlow Hill (Cambs). Zone of 
Holaster planus of Chapel Rock (Pinhay), Dover, the Sussex coast, Cheveley, and 
Linton. Chalk Rock (Iewssianwm-zone) of Brixton, Winchester, Cuckhamsley, 
Thickthorn Hill, and Boxmoor. 
(iii) Upper Chalk: Zone of M. cor-testudinarium of Dover, the Sussex coast, and 
Balsham. Zone of M. cor-anguinum of Thanet, St. Margaret’s, the Sussex coast, 
Charlton, Gravesend, Strood, Northfleet, and near Hitchin. Zone of Marsupites of 
Thanet and the Sussex coast. Zone of A. quadratus of Henstmg Farm, Marwell 
Road, and Hensley Lane (all near Winchester), Hast and West Harnham (near 
Salisbury), and the Sussex coast. Zone of B. mucronata of the Dorset coast. 
SPONDYLUS SERRATUS, sp. nov. Plate XXI, figs. 6 a—c, 7 a—e. 
Description.—Shell rounded, outline rather irregular, slightly mequilateral ; 
height and length nearly equal. 
Right valve flattened or slightly concave, with numerous parallel, concentric, 
and spiny laminge and faint radial ribs. 
Left valve moderately convex, except in small forms ; ornamented with numerous 
small ribs, which are of equal size except on the earlier parts of the shell, where 
new ribs are being introduced ; all the ribs bear many small spines, placed regularly, 
but on the old parts of the shell the ribs may be nearly smooth. The grooves are 
broader than the ribs, moderately deep, and crossed by well-marked but somewhat 
irregular, transverse, thread-like ribs. Ears with four or five ribs. 
Measurements : 
(1) (2) (3) 
Length . , > XO) : 5 OB ; . o2mm. 
Height. 5 2 AGES : . 23 : > 29° 55 
(1) Upper Chalk (Uintacrinus-bed), Devizes Road, Salisbury. 
(2) Upper Chalk, locality unknown. 
(8) Upper Chalk (Uintacrinus-bed), Newgate, Thanet. 
Affinities. —This is similar in form to S. latus, but is distinguished by the small 
and regular spines, and the broader grooves between the ribs. S. Royanus, 
