ORDOVICIAN BRACHIOPODA 33 



SJ 309012) ; BB 37113, 371 15 from outcrops 80 yds from Meadowtown Quarry 

 along Rorrington road (Grid Ref. SJ 311013) ; BB 37110 from outcrops along lane 

 to Lower Ridge from benchmark 754, Little . Weston (Grid Ref. SO 293984) ; 

 BB 37109 from outcrops in Lower Wood Brook 400 ft south-east of the Meadow- 

 town -Rorrington road (Grid Ref. SJ 307008) ; BB 371 12 from laneside exposures 

 370yds north of Meadowtown Chapel (Grid Ref. SJ311015). Betton Beds: 

 BB 37116, 37117 from outcrops downstream of junction between Holywell and 

 Whitehouse Brooks (Grid Ref. SJ 303004) ; exact locality of BB 371 16 uncertain. 

 Rorrington Beds : BB 37118 from exposures in a stream 530 yds north-west of 

 Meadowtown Chapel (Grid Ref. SJ 308017). 



Palaeoglossa myttonensis sp. nov. 

 (PI. 4) figs. 1-5) 



Diagnosis. Ventribiconvex Palaeoglossa with a brachial valve 78% as wide and 

 4% as deep as long and a pedicle valve about twice as deep ; fila fine and normally 

 continuous ; dorsal pseudointerarea lenticular and restricted to the umbonal area, 

 dorsal median septum extending anteriorly for about half the valve length ; postero- 

 medial internal surfaces of shell sporadically and shallowly pitted. 



Description. Ventribiconvex, oval Palaeoglossa with curved lateral and rounded 

 anterior margins ; brachial valve 78% as wide and 4% as deep as long, pedicle 

 valve about 8% as deep as long ; both valves evenly convex in longitudinal and 

 transverse profiles ; surfaces ornamented by growth lines and fine, somewhat 

 distant, more or less continuous fila with a wavelength of about 0-25 mm. 



Ventral pseudointerarea striated, slightly anacline, crescentic, divided by a 

 shallow pedicle trough extending anteriorly for 11% of the length of the valve. 



Dorsal pseudointerarea striated, slightly anacline, lenticular in outline, restricted 

 to the umbonal area and extending anteriorly for 9% of the valve length ; dorsal 

 median ridge low, extending forward for 51% of the valve length (range 47% to 

 54% for 5 specimens) ; postero-medial internal surfaces of both valves sporadically 

 and shallowly pitted. 



Type material. 



length width (mm) 

 Holotype External and internal moulds of conjoined 



valves (BB 37119) - 4-5 



Paratypes Incomplete external and internal moulds of 



brachial valve (BB 37121a, b) - - 



External and internal moulds of slightly 

 disarticulated valves (BB 37122a, b) 6-5 5-0 



Internal mould of brachial valve (BB 37123) 6-5 5-2 



Horizon and localities. Mytton Flags : BB 37119, 37122 from tip heaps on 

 road to Squilver 150 yds ENE of Whitegrit School (Grid Ref. SO 323976) ; BB 37121 

 from sides of adit of New Perkin's Level (Grid Ref. SJ 376022) ; BB 37123 from 



