PECTEN. 



151 



ears mucli larger than nsnal, also a smaller apical angle, and straight nntero- and 

 postero-dorsal margins ; the shell is rather high in proportion, and the ribs are 

 nnraerous. Since all the Haldon specimens agree in these respects, and are readily 

 distingnishable from those found elsewhere, they may be regarded as a local 

 variety, and named P. orhlcnlaris, var. haldonensis : this variety resembles the form 

 from the Cenomanian of Bavaria figured by S(")hle (1897). The forms fonnd in 

 the Upper Greensand of Warminster are rather larger than most of tliose in the 

 Gault and Lower Cretaceous, and often have numerous ribs. 



5. Cenomanian. — Small forms, with a variable number of ribs, occur commonly 

 in the Chalk Marl, and rarely also a very large variety, sometimes reaching 70 mm. 

 in height (Text-fig. 1). In the fl. suhglohosus zone the average size is rather 



Fio. 1. — Pecten (Syncydoiiema) orhicula 



Sow. Chalk Marl, Folkestone. 

 Natural size. 



Woodwardian Museum. 



larger than in Gault and Lower Cretaceous, but no forms as large as those in the 

 Upper Greensand mentioned above have been seen. The number of ribs is 

 variable. 



Types. — The type, from the Upper Greensand of Devizes, appears to have been 

 lost, and the same is the case with the types of P. laniinosns from the Chalk Marl 

 of Hamsey and Stoneham. 



Distrihntlon. — Folkestone Beds of Folkestone. liOwer Greensand of Upware. 

 Spilsby Sandstone of Donnington and Spilsby. Claxby Ironstone of Benniworth 

 Haven. Tealby Limestone (zone of B. brunsvicensis) of North Willingham and 

 Claxby. Speeton Series (same zone) of Speeton {fide Lamplugh). 



Also recorded in the Geological Survey Memoirs from the Perna-hed of Ather- 



