ORDOVICIAN BRACHIOPODA 41 



9% of the length of the brachial valve forward of the truncated posterior margin ; 

 limbus well developed. 



Description. Dorsibiconvex, elongately oval Paterula with a slightly truncated 

 posterior margin and a rounded anterior one, brachial valve with a mean width 

 relative to length of 87% (range 82% to 90% for 7 valves) and a mean depth relative 

 to length of 17% (range 15% to 20% for 5 valves), pedicle valve with a mean depth 

 relative to length of 8% for 2 valves ; surface ornamented by fine concentric lines ; 

 pedicle notch wide, immediately posterior of ventral beak ; submarginal dorsal 

 beak located, on average, 9% of the length of 3 brachial valves (range 7% to 10%) 

 forward of their posterior margins and not constituting the greatest depth of the 

 valve which is in mid-region. 



Limbus well defined in both valves about 7% as wide as the valves are long ; 

 other internal features unknown except for two lines diverging from the ventral 

 beak and bounding a faint median ridge. 



Figured material. 



length width (mm) 



Exterior of pedicle valve (BB 35590) i-6 1-5 



Exterior of brachial valve (BB 35591) 1-8 i-6 



Exterior of pedicle valve (BB 35592) i-6 1-5 



Exterior of pedicle valve (BB 35593) i-6 1-4 



Exterior of brachial valve (BB 35594) 1*9 1-9 



Incomplete exterior of brachial valve (BB 35595) - 1-9 



External and internal moulds of pedicle valve (BB 35588a, b) 2-0 1-9 



External and internal moulds of brachial valve (BB 35589a, b) i-6 1-4 



Horizons and localities. BB 35590 to 35595 inclusive from Meadowtown 

 Beds exposed 100 yds south-east of Minicop farm (Grid Ref. SJ 315018) ; BB 35588, 

 35589 from Hope Shales exposed in Hope Dingle behind Hope Cottage (Grid Ref. 

 SJ 338009). 



Paterula cf. perfecta Cooper 

 (PL 6, figs. 12, 13) 

 1956 Paterula perfecta Cooper : 258. 



Diagnosis. Elongately oval Paterula with a brachial valve 88% as wide as long 

 and 20% as deep as long, ventral beak submarginal, dorsal beak 23% of the length of 

 the brachial valve forward of the rounded posterior margin ; limbus becoming 

 subdued anteriorly. 



Description. Dorsibiconvex, elongately oval Paterula with rounded posterior 

 and anterior margins, brachial valve with a mean width relative to length of 88% 

 (range 80% to 90%) and a mean depth relative to length of 20% (range 20% to 21%) 

 for 4 valves ; pedicle valve with a mean depth relative to length of 11% (range 10% 

 to 11%) for 3 valves ; surface ornamented by fine concentric lines ; pedicle notch 

 small, ventral beak submarginal, located on average 10% of the length of 3 pedicle 



