PECTEN. 165 
Measurements : 
(1) (2) (3) (4) (5) (6) (7) 
Leneth . 45 . 40 . 36 . 06 . 35 . 27 . 26 mm. 
Height . 52 . 47 . 445 . 44 . 42 . 31 . 29 
(1) Totternhoe Stone, Cherry Hinton. 
(2—7) 5 5 surwell. 
29 
Affinities. —P. fissicosta is readily distinguished from the other species with 
strong ribs by its numerous radial striae and by the fission of some of the main 
ribs. P. landeronensis, De Loriol,! resembles this species in form, but possesses a 
strongly marked concentric ornamentation. The radial striae of I’. fissicosta 
resemble those of Camptonectes as well as those seen in [’. Robinaldinus, ete. The 
varieties, with few and undivided ribs (Pl. XXX, fig. 7), approach P. decencostatus, 
Goldfuss (references on p. 167), but the valves are higher. 
T'ypes.—F rom the Totternhoe Stone, Burwell; in the Woodwardian Museum. 
Distribution.—Chloritic Marl of Ventnor. Chalk Marl of Egeardon Hill 
(Dorset), Folkestone, and Blue Bell Hill, Burham. Totternhoe Stone of Arlesey, 
Cherry Hinton, Burwell, Orwell, and Stoke Ferry. Zone of H. subglobosus of 
Cherry Hinton. 
Precren (Cutamys) Puzosianus, Matheron, 1842. Plate XXX, figs. 9a, b, 10a, b, 
lesion 
1842. Prcren Puzostanus, P. Matheron. Catal. Foss. des Bouches-du-Rhone, 
p. 185, pl. xxx, figs. 1—3. 
1847. — — A. @Orbigny. Pal. Franc. Terr. Crét., vol. iii, p. 610, 
pl. ceeexxxvii, figs. 1—4. 
1850. — _ — Prodr. de Pal., vol. ii, p. 197. 
1870. — — PF. J. Pictet and G, Campiche. Foss. Terr. Crét. Ste. 
Croix (Matér. Pal. Suisse, ser. 5), p. 215. 
1896. — ef. Puzostanus, A. J. Jukes-Browne and W. Hill. Quart. Journ. 
Geol. Soe., vol. ii, p. 151. 
Deseription.—Shell ovate, higher than long, nearly equilateral and equivalve, 
dorsal portion pointed; antero- and postero-dorsal margins long. Convexity 
small, valves bent near the antero- and postero-dorsal margins. Apical angle about 
90°. Kars large, unequal. 
Right valve shghtly convex, with numerous narrow ribs, which on the mid- 
dorsal parts of the valve are alternately large and small, but elsewhere become 
‘ De Loriol and Gilliéron, ‘ Urgon. Infér. de Landeron’ (1869), p. 22, pl. i, fig. 19; Pictet and 
Campiche, “Terr. Crét. de Ste. Croix”’ (‘ Mater. Pal. Suisse,’ ser. 5, 1870), p. 187, pl. elxix, figs. 6, 7. 
