76 SHELVE DISTRICT 



Type horizon and locality. Meadowtown Beds exposed in a small excavation 

 in the corner of a field alongside the cart-track from Meadowtown to Waitchley, 

 330 yds south of Waitchley (Grid Ref. SJ 311017). 



Discussion. Although the moulds of only one pedicle and one brachial valve of 

 Tazzarinia have been recovered from the Meadowtown Beds, there is no doubt about 

 their generic affiliations or their specific distinctiveness. The specimens compare 

 in every important respect with the Tazzarinia described by Havlicek (1971 : 39) 

 from the Lower Caradoc of Morocco except that bilobation of the cardinal process 

 cannot be confirmed in the Shropshire dorsal mould. Yet the Shelve form is im- 

 mediately distinguishable from both Moroccan species, T. drotae and T. foraminosa, 

 especially in its coarsely fascicostellate ornamentation and its elongately subquadrate 

 outline. 



Subfamily PLATYSTROPHIINAE Schuchert & Le Vene 1929 



PLATYSTROPHIA King 1850 



Platystrophia caelata sp. nov. 



(PI. 12, figs. 13, 14, 16-19) 



Diagnosis. Subquadrate, dorsibiconvex Platystrophia with the pedicle valve 

 76% as long as wide and 32% as deep as long, with a flat-bottomed sulcus 54% as 

 wide as the valve length, ornamented by 2 costae in the sulcus and 10 to 14 on the 

 lateral slopes with lamellae extending along the crests of costae as short rounded 

 canopies. 



Description. Subquadrate, dorsibiconvex, uniplicate Platystrophia with sub- 

 rectangular cardinal angles, the brachial valve just over two-fifths as deep as long, 

 the pedicle valve on average 76% (range 70% to 79%) as long as wide and 32% 

 (range 28% to 35%) as deep as long for 3 valves, with a flat-bottomed sulcus with a 

 mean width of 54% (range 50% to 57%) relative to the length for 3 valves, and 

 evenly convex lateral slopes ; dorsal interarea short, anacline, ventral interarea 

 curved, apsacline about one-fifth as long as pedicle valve ; costae angular with a 

 wavelength of just over 1 mm, 5 mm anterior of dorsal umbo, covered with densely 

 distributed tubercles and numbering 2 in the ventral sulcus with 10 to 14 on the 

 lateral slopes ; lamellae strongly developed and, beyond 4 mm from umbones, 

 extending along the crests of the costae as short, rounded canopies partially covering 

 subtriangular concave pads of secondary shell. 



Ventral interior with small pedicle callist, thick teeth supported by short, receding 

 dental plates extending anteriorly for less than one-fifth the length of the pedicle 

 valve, and subtriangular muscle field with wide adductor impressions occupying the 

 floor of the valve, less than half as wide as long and extending anteriorly for just 

 over two-fifths the length of the pedicle valve ; mantle canal impressions obscure 

 but ventral system possibly digitate with abbreviated vascula media occupying the 



