30 SHELVE DISTRICT 



gently and evenly convex in longitudinal and transverse profiles ; external surface 

 ornamented by concentrically disposed impersistent lamellae giving a finely scalloped 

 appearance ; ventral beak sharply acute, dorsal beak less conspicuous and more 

 rounded. 



Ventral pseudointerarea striated, anacline to orthocline, crescentic in outline and 

 divided into two obliquely disposed propareas by a shallow pedicle groove extending 

 forward for about 13% of the valve length ; ventral muscle impressions unknown. 



Dorsal pseudointerarea striated, orthocline, lenticular in outline and extending 

 forward for 5% of the valve length ; dorsal muscle impressions unknown ; fine 

 median ridge faintly developed for over half the valve length, postero-medial internal 

 surfaces of both valves sporadically and shallowly pitted. 



Type material. 



length width (mm) 

 Holotype External and internal moulds of pedicle valve 



(BB 37150a, b) io-o 6-0 



Paratypes External and internal moulds of brachial valve 



(BB 37151a, b) 8-o 6-o 



External and internal moulds of pedicle valve 



(BB 37152a, b) - 6-o 



Type horizon and locality. All specimens from the Stapeley Volcanic Group 

 exposed in Whitsburn Dingle, 650 yds WS W of Lord's Stone, Leagh (Grid Ref . 

 SJ 328019). 



Discussion. Ordovician Lingulella from the Shelve area appear to differ from 

 other known Lingulella in being ornamented by finely scalloped lamellae. The pat- 

 tern is reminiscent of Glyptoglossella although in other respects, notably the presence 

 of a dorsal pseudointerarea, the specimens cannot even be assigned to the same sub- 

 family. The change in outline from oval to subtriangular that took place during the 



Table 13 



Statististics of length (1) and maximum width (w) of n brachial valves of Lingulella displosa sp. 

 nov. from the Rorrington Beds (A) and the Meadowtown Beds (B) 



A B 



n 12 8 



1 mm (var 1) 8-84 (14-383) 8-05 (25-209) 



w mm (var w) 8-6 (13-647) 6-97 (19-902) 



r 0-986 0-97 



a (var a) 0-9741 (0-00269) 0-8885 (°' 00 774) 



Table 14 



Statistics of length (1) and maximum depth (w) of 8 pedicle valves of Lingulella displosa sp. nov. 



from the Rorrington Beds 



1 mm (var 1) 4-76 (8-931) 



w mm (var w) 4-37 (8-494) 



r 0-994 



a (var a) 0-9752 (0-00184) 



