ORDOVICIAN BRACHIOPODA 27 



becoming less distinct medially, and finely developed overlapping lamellae ; however 

 the thin shell is usually preserved in a collapsed state commonly expressed as trans- 

 verse or even radiating wrinkles. 



Ventral interior with a narrow crescentic striated pseudointerarea divided by a 

 relatively wide pedicle groove ; muscle impressions known only in one specimen as a 

 pair of suboval, submedial scars, possibly flanked by another set, distinguishable as 

 smooth areas in a finely pitted internal surface. 



Dorsal pseudointerarea with a very narrow thickened zone along the posterior 

 margin which may represent a medially grooved pseudointerarea ; other internal 

 features unknown although a low median ridge extends forwards for three-quarters 

 the length of some valves. 



Type material. 



length width (mm) 

 Holotype External and internal moulds of pedicle valve 



(BB 37134a, b) 4-5 4-5 



Paratypes External and internal moulds of brachial valve 



(BB 37135a, b) 



Exterior of pedicle valve (BB 37136) 



External and internal moulds of pedicle valve 



(BB 37137a, b) 



Internal mould of brachial valve (BB 37138) 



Internal mould of pedicle valve (BB 37139) 



External and internal moulds of pedicle valve 



(BB 37140a, b) 3-5 3-5 



Horizon and localities. Rorrington Beds : BB 37134, 37138 from exposures 

 in Holywell Brook 160 yds WNW of the Mount, Rorrington (Grid Ref. SJ 299007) ; 

 BB 37135, 37139 from outcrops in Deadman's Dingle 100 ft upstream from junction 

 with Spy Wood Brook (Grid Ref. SO 280960) ; BB 37136 from exposures 60 yds 

 north-west of the Mount, Rorrington (Grid Ref. SJ 302005) ; BB 37137, 37140 from 

 the tributary to Lower Wood Brook 340 yds south-east of Desert (Grid Ref. 

 SJ 308017). 



Schmidtites ? simplex subcircularis sp. et subsp. nov. 

 (PL i, figs. 16, 17 ; PI. 2, fig. 1) 



Diagnosis. Like Schmidtites ? simplex but subcircular with valves 96% as wide 

 as long and 7% as deep as long ; protegulum semicircular about 0-2 mm long. 



Type material. 



length width (mm) 

 Holotype Exterior of pedicle valve (BB 37141) 2-5 2-8 



Paratypes External and internal moulds of pedicle valve 



(BB 37142a, b) 3-0 3-0 



External and internal moulds of brachial valve 



(BB 37143a, b) 3-3 3-6 



3-o 



27 



3-5 



4-0 



2-6 



— 



4-2 



4-5 



4-0 



- 



