ORDOVICIAN BRACHIOPODA 127 



median adductor impression divided by divergent vascula media. Dorsal interior 

 unknown. 



Figured material. 



length width (mm) 

 External and internal moulds of pedicle valve (BB 35415a, b) 8-0 14-0 



External and internal moulds of pedicle valve with adherent 

 shell (BB 35451a, b) 10-5 



External moulds of shell (BB 35414a, b) 7*5 14-0 



Horizon and localities. Whittery Shales : BB 35415 from exposures half-way 

 down path below Marrington Farm going southwards (Grid Ref. SO 272967) ; 

 BB 35451 from the lower part of the succession in the west bank of the River Camlad, 

 60 yds north-east of Marrington Farm (Grid Ref. SO 272970) ; BB 35414 from 

 Whittery Quarry at the south end of Whittery Wood near Chirbury (Grid Ref. 

 SO 275981). 



Discussion. Despite the apparent absence of accessory teeth in the pedicle valve 

 and the lack of information about the dorsal interior, a few strophomenide moulds 

 recovered from the Whittery Shales may be safely assigned to Palaeostrophomena in 

 the wider interpretation of that genus (Williams in Whittington & Williams 1955 : 

 415). In known characteristics, the specimens compare closely with P. magnified 

 from the Derfel Limestone of N. Wales as well as certain Scottish species from the 

 Ardmillan Series of Scotland (Williams 1962 : 158), so that specific identification is 

 not possible until more material is available. 



Family EOCRAMATIIDAE nov. 



Diagnosis. Plectambonitaceans (?) with a complementary pseudodeltidium and 

 chilidium, a small submesothyridid foramen, unsupported simple teeth, strong 

 narrowly divergent chilidial plates (?) filling the notothyrium in place of a discrete 

 platform and continuous with widely splayed cup-shaped socket ridges ; shell 

 impunctate. 



Discussion. There are many features of the new genus Eocramatia that reflect 

 the tendency of related major groups to show morphological convergence as they are 

 traced back towards their common ancestry. The presence of a pseudodeltidium 

 and chilidium indicates affinities with the Clitambonitidina, Strophomenidina and 

 Billingsellacea. But the absence of dental plates and the structure of the cardinalia 

 preclude assignment of the genus to the Clitambonitidina, and although the im- 

 punctate condition of the shell and the morphology of the pedicle valve suggest that 

 Eocramatia was derived from the billingsellaceans, many dorsal features contradict 

 this interpretation. These include the absence of an orthide notothyrial platform, 

 and the nature of the divergent plates filling the notothyrium and their relationship 

 to the socket ridges. In all, then, it seems that it can be fairly confidently assigned 

 to the Strophomenidina. 



