66 SHELVE DISTRICT 



Specimens of Glyptorthis recovered from the Whittery Shales and Meadowtown 

 Beds may, provisionally at least, be referred to the new species despite minor 

 differences in morphology. 



The few moulds known from the younger formation include only one external 

 mould of a brachial valve large enough to provide data about ornamentation. 

 Counts of 2 per mm at 5 mm antero-medially of the umbo were obtained for both 

 radial and concentric ornamentation and are smaller than those for G. viriosa s.s. In 

 all other features, however, the shells must have been indistinguishable from the 

 Spy Wood forms and more information is necessary to establish the significance of 

 the difference. 



The more frequently occurring Glyptorthis from the Meadowtown Beds, on the 

 other hand, is identical with the new species except for the size of the cardinalia 

 which extend anteriorly for only 10% of the length of the two known brachial valves. 

 This size relationship is subnormal for brachial valves of comparable length in the Spy 

 Wood sample, although more specimens are needed to assess the significance of the 

 difference. Two specimens are figured (PI. 10, fig. 15 ; PL 11, figs. 1, 2, 4) : a 

 brachial valve (BB 35520a, b) from loose flags by the side of Minicop Farm (Grid 

 Ref. SJ 314018), and a pedicle valve (BB 35521a, b) from Quinton's Quarry in the 

 field 200 yds north-east of Meadowtown Chapel (Grid Ref. SJ 312013). 



Table 43 



Statistics of length (1) and maximum width (w) of 17 brachial valves of Glyptorthis viriosa sp. nov. 



1 mm (var 1) 4-23 (3-037) 



w mm (var w) 5-26 (3-424) 



r 0-978 



logel (var log e l) 1-3637 (° -I 567) 



logeW (var log e w) 1-6029 (0-1165) 



r e 0-981 



a (var a) 0-8621 (0-00191) 



Table 44 



Statistics of length (1) and maximum depth (th) of 19 brachial valves of Glyptorthis viriosa sp. nov. 



1 mm (var 1) 4-28 (3-05) 



th mm (var th) 0-97 (0-162) 



r o-866 



a (var a) 0-2306 (0-00078) 



Table 45 



Statistics of length (1) and maximum depth (th) of 23 pedicle valves of Glyptorthis viriosa sp. nov. 



1 mm (var 1) 3-46 (4-857) 



th mm (var th) 1-27 (0-594) 



r 0-945 



a (var a) 0-3497 (0-00061) 



