





PECTEN. 











ensurements . 



















(1) 



(2) 



(3) (1) 



(5) 



(«) 



(7) 





Length . 



4-5 



. 40 . 



o(') . ;3() 



. ;}5 



. 27 , 



. 20 



mil 



Hoio-ht . 



52 , 



, 47 . 



44-5 . 44 , 



. 42 , 



. 31 , 



. 2U 





1G5 



(1) Tottenilioe Stone, Cherry Hiutou. 

 (2—7) „ „ Burwell. 



AJfiulties. — P. fisslcosta is readily distinguished from the other species with 

 strong ribs by its numerous radial strise and by the fission of some of the main 

 ribs. P. landeroneusls, De Loriol,' resembles this species in form, but possesses a 

 strongly marked concentric ornamentation. The radial strise of P. Jissicosta 

 resemble those of Camptoiiedes as well as those seen in 1\ Bohinaldimis, etc. The 

 varieties, with few and undivided ribs (PI. XXX, fig. 7), approach /'. dcccnicostaius, 

 Goldfuss (references on p. 167), but the valves are higher. 



Ti/pes. — From the Totternhoe Stone, Burwell ; in the Woodwardian Museum. 



Distribution. — Chloritic Marl of Ventnor. Chalk Marl of Eggardon Hill 

 (Dorset), Folkestone, and Blue Bell Hill, Burham. Totternhoe Stone of Arlesey, 

 Cherry Hinton, Burwell, Orwell, and Stoke Ferry. Zone of 11. sidiglohosas of 

 Cherry Hinton. 



Pkoten (Chlamys) PuzosiANUS, Mathcron, 1842. Plate XXX, figs, da, h, 10 a, h, 



11, 12. 



1842. Pecten PuzosiANUS, P. MatheroH. Catal. Foss. cles Bouches-du-Eliouo, 



p. 18.5, pi. XXX, figs. 1—3. 

 1847. — — A. (VOrhljinj. Pal. Fran9. Terr. Crct., vol. iii, p. 610, 



pi. ccccxxxvii, figs. 1 — 4. 

 1850. — — — Prodr. de Pal., vol. ii, p. 197. 



1870. — — F.J. Plcttt and O. Campiclie. Foss. Terr. Crct. Ste. 



Croix (Mater. Pal. Suisse, ser. 5), p. 215. 

 1896 — cf. PuzosiANUS, A. J. Juices-Browne and W. Hill. Quart. Jouru. 



Geol. Soc, vol. lii, p. 151. 



Descrijjlion. — Shell ovate, higher than long, nearly equilateral and e(|uivalve, 

 dorsal portion pointed ; antero- and postero-dorsal margins long. Convexity 

 small, valves bent near the antero- and postero-dorsal margins. Apical angle about 

 90°. Ears large, unequal. 



Right valve slightly convex, with numerous narrow ribs, which on the mid- 

 dorsal parts of the valve are alternately large and small, but elsewhere become 



■ De Loriol aud Gillieron, ' Urgou. Infer, de Landeron' (1869), p. 22, pi. i, fig. 19; Pictet and 

 Oauipiehe, "Terr. Cret. de Ste. Croix" ('Mater. Pal. Suisse,' ser. 5, 1870), p. 187, pi. clxix, figs. 6, 7. 



