ORDOVICIAN BRACHIOPODA n 



ABCDEFGHI JK 



Schmidtites ? simplex sp. nov. ____ r r f c _ f c _ _ 



Schmidtites ? simplex subcircularis sp. et 



subsp. nov. r _f c -------- 



Sericoidea cf . abdita Williams _________ r _ 



Skenidioides cf. costatus Cooper — — — — — — rfc — — c 



Sowerbyella cf. antiqua Jones _____ r _____ 



Sowerbyella multiseptata sp. nov. _______ c ___ 



Sowerbyella cf . sericea permixta Williams ________ f c __ 



Sowerbyella cf . sericea (Sowerby) --------- fcvc 



Sowerbyella sp. ______ r ____ 



Tazzarinia elongata sp. nov. _____ r _____ 



Tissintia immatura (Williams) _____f c _____ 



Tissintia prototypa (Williams) ---cfc ------ 



Triplesia sp. __________ r 



Whittardia paradoxica gen. et sp. nov. __________ c 



Zygospira sp. _______ r ___ 



The list does not include the few poorly preserved inarticulate brachiopods 

 recovered from the Stiperstone Quartzite which were : a discinid, an obolid and 

 Pseudolingula sp. 



The large number of identifications reflect the assiduity of the collectors and the 

 great range of geologic time represented by the strata from which specimens have 

 been recovered, rather than any intrinsic richness of faunas. Compared with 

 contemporaneous faunas from Scotland or the Baltic, for example, the Shelve 

 assemblages are restricted in content. This relative paucity may be illustrated 

 (Text-fig. i) by estimating the number of species recorded per 300 m of rock for 

 each formation, using thicknesses given by Watts (1925) and Whittard (1952). The 

 greatest diversity of about 76 species per 300 m for the Whittery Shales is only 

 one-third that calculated for the penecontemporaneous Balclatchie Mudstones 

 (Williams 1962 : 27). This contrast is further emphasized by the negligible taxo- 

 nomic communality, even at generic level, between the Shelve assemblages and 

 coeval Scottish or Baltic ones, and appears to be related to profound environmental 

 differences ranking with provincial distinctions (Williams 1973 : 246) in Recent seas. 

 Accordingly only assemblages found in Wales, E. Shropshire and, to a lesser extent, 

 N. Africa and Bohemia are like those of the Shelve area ; and even these show 

 discrepancies in stratigraphic distributions and frequencies of occurrence probably 

 linked to the benthic habits of brachiopods. 



The brachiopods occurring in the Mytton Flags have an Arenigian aspect even in 

 relation to assemblages characteristic of more remote regions. Desmorthis, Dipare- 

 lasma and Hesperonomia are reminiscent of American successions (Ulrich & Cooper 

 1938 : 27-28) ; Orthis callactis (Rubel 1961 : 142) and Oslogonites (Opik 1939 : 118) 

 of the Baltic region ; and Euorthisina and Nocturniella (Havlicek & Vanek 

 1966 : 50) of Czechoslovakia, although the species with which the Shelve Euorthisina 

 has been compared occurs in the Llanvirnian Sarka Formation of Bohemia and the 

 Llanvirnian Tachilla Shales of Morocco (Havlicek 1971 : 75). With respect to more 

 precise correlation with other Anglo- Welsh successions, only Lenorthis proava has 



