ORDOVICIAN BRACHIOPODA 105 



umbones of 4 and 3 brachial valves, external branching poorly developed but pro- 

 gressively earlier in lateral sectors. 



Teeth strong with well-developed crural fossettes supported by divergent dental 

 plates with an average forward extension relative to the length of 6 pedicle valves 

 of 19% (range 17% to 22%) ; ventral muscle scar bilobed, 83% as wide as long in 12 

 pedicle valves (range 72% to 104%), extending anteriorly for 34% of the length of 

 7 valves (range 28% to 39%) and consisting of a broad median adductor impression 

 not enclosed by subtriangular diductor tracks ; mantle canal system probably 

 lemniscate. 



Cardinal process consisting of a massive shaft with serrated ridge-like myophore 

 embedded in a thickened notothyrial platform indented anteriorly by shallow pits 

 for the insertion of adductor muscle bases ; brachiophores divergent, blade-like 

 defining crenulated sockets ; muscle impressions unknown. 



Type material. 



Holotype External and internal moulds of pedicle valve 



(BB 35513a, b) 

 Paratypes External and internal moulds of brachial valve 



(BB 35514a, b) 



Incomplete external mould of pedicle valve 



(BB 35515) 



Incomplete internal mould of brachial valve 



(BB 35516) 



Incomplete external and internal moulds of 



pedicle valve (BB 35517a, b) 



Incomplete external and internal moulds of 



brachial valve (BB 35518a, b) 



Incomplete external and internal moulds of 



brachial valve (BB 35519a, b) 



Horizon and localities. Whittery Shales : BB 35516 and BB 35519 from 

 exposures about half-way down path going south to valley bottom below Marrington 

 Farm (Grid Ref. SO 272967) ; the remainder from lower part of western bank of 

 River Camlad 60 yds north-east of Marrington Farm (Grid Ref. SO 272970). 



Discussion. The Reuschella occurring in the Whittery and Hagley Shales are 

 related to the early Caradocian R. horderleyensis (s.l.) which is widespread in E. 

 Shropshire and Wales (Bancroft 1945:239; Williams 1963:413). However, 

 comparisons with R. cf. horderleyensis and R. horderleyensis undulata from the Bala 

 area (Williams 1963 : 415-417) show differences exist which merit taxonomic 

 recognition. In the outline of the shell and of the ventral muscle scar and its forward 

 extension as well as the texture and branching of their radial ornamentation, the 

 Shelve specimens are indistinguishable from R. horderleyensis and the Welsh sub- 

 species. They do, however, differ from both taxa in being much flatter laterally 

 and additionally from R. horderleyensis in the growth of the cardinalia. It seems 



length 



width (mm) 



13-5 



17-0 



13-5 



19-0 



13-5 



- 



13-0 



- 



13-5 



- 



12-5 



- 



4-0 



- 



