44 SHELVE DISTRICT 



length width (mm) 



Paratypes External mould of brachial valve (BB 35567) 3-0 3-5 



Internal mould of brachial valve (BB 35568) 3-2 37 



Internal mould of brachial valve (BB 35569) 2-2 2*5 

 Internal mould of brachial valve with 



adherent shell (BB 35570) 3-2 3-5 

 External and incomplete internal mould of 



pedicle valve (BB 35571a, b) 3-5 37 



Horizon and locality. Stapeley Shales exposed on the road side north-east of 

 bench mark 412-5, Leigh Hall (Grid Ref. SJ 334036). 



Discussion. A small number of acrotetid moulds recovered from the Stapeley 

 Shales appear to constitute a new species of Conotreta. In the absence of precise 

 data, no comparison can be drawn between the Stapeley Conotreta and other described 

 species in respect of the shape of the shell and its principal morphological features. 

 However, a combination of some of the basic characters of the genus immediately 

 separate C. stapeley ensis from American (Cooper 1956 : 247-255), Baltic (Goryanski 

 1969 : 62-65) an( i Scottish (Williams 1962 : 90) Conotreta. Such features include the 

 development of a deltoid arch in place of an intertrough dividing a predominantly 

 procline ventral pseudointerarea, and the late division of the submedial vascula 

 later alia. 



The complementary moulds of a brachial valve which is likely to belong to 

 Conotreta have also been found in the Hope Shales ; but, in the absence of an 

 associated pedicle valve, its specific affinities cannot be determined. 



Superfamily DISCINACEA Gray 1840 



Family TREMATIDAE Schuchert 1893 



SCHIZOCRANIA Hall & Whitfield 1875 



Schizocrania salopiensis sp. nov. 



(PI. 6, figs. 22-26) 



Diagnosis. Schizocrania with subcircular brachial valve about one-third as 

 deep as long with posteriorly placed umbo and dichotomizing radial capillae com- 

 monly 8 to 10 per mm, 5 mm antero-medially of umbo ; large posterior adductors 

 extending anteriorly for one-third the length of the valve. 



Description. Brachial valve subcircular and deep being 86% as long as wide 

 and 33% as deep as long, transverse profile evenly convex, longitudinal profile 

 asymmetrically convex with the posteriorly placed umbo overhanging a strong 

 groove indenting the posterior part of the valve just within the smoothly rounded 

 posterior margin ; exterior ornamented by sporadically occurring growth lines and 

 capillae disposed radially from the umbo, curving to intersect the posterior margin, 

 and branching by subequal dichotomy and commonly numbering 10 per mm, 5 mm 

 antero-medially of the umbo ; dorsal interior with thickened rounded posterior 

 margin extending postero-laterally for over four-fifths the width of the valve. 



