Yol. 62.] IN THE CARBONIFEROUS ROCKS AT RUSH. 309 



Schizophoria resupixata (Martin). 



This gens occurs rarely in the Megastoma-~Beds, but abundantly 

 in the Cyatliaxonia-Be&s and in the Curkeen Limestone. 



In the upper beds, the gens strikingly exhibits that exaggeration 

 of characters which so frequently indicates approaching extinction. 

 Great size and massive test, periodicity of ribbing accompanied by 

 the development of prominent spines, numerous strongs-marked 

 growth-lines producing conspicuous concentric ornament, deep sul- 

 cation of the brachial valve, and coarse longitudinal grooving (as 

 in the Choneti-Productids of the same period), are among the most 

 striking of the external characters. As regards internal characters, 

 the muscular scars are deeply impressed and of large size ; the cast 

 exhibits strong, sharp, longitudinal ridges and a coarsely-punctate 

 margin. 



In the South- Western Province, as already noticed, no typical 

 specimens of Schizophoria resupinata have yet been found in the 

 Upper Avonian ; the Lower Syringothyris-Zone is the only level at 

 which typical examples are abundant. The early variant which 

 characterizes Z 2 of that area is distinguished from the type-species 

 by its small size and non-sulcate globose form. 



On the other hand, every variation exhibited by the gens in the 

 Cyathaxonia-'Beds of Rush and in the Curkeen Limestone could be 

 matched in specimens from the Wetton and Park-Hill Beds of the 

 Midlands. 



Schizophoria l sp. 



In the Curkeen Limestone, and associated with Scliizoplioria 

 resupinata, occurs a small Orthid, whicb has a globose brachial valve 

 and a flattened pedicle-valve. The hinge-line is short, as in a 

 Ithipidomella, and the ribbing is of the type characteristic of that 

 genus. 



A closely-similar form occurs in the uppermost Avonian of 

 Eagwen Point, near Tenby. 



Orthothetes (Derbya) sexilis (Phil.), var. (?)anomala (J. Sow., 

 pars). 



Compare Derbya ruginosa, Hall. 



Specimens are not uncommon in the Curkeen Limestone which 

 have the characteristic billowy contortion ; when sectioned, the 

 pedicle- valve exhibits the strong mesial septum which is diagnostic 

 of Waagen's genus Derby a. 



Exactly-similar specimens are common at Park Hill (Midland 

 area). At the base of D 1? in the South-Western Province, a 



1 This shell might equally well be termed a Bhipidomella. It is very 

 doubtful whether, in the Carboniferous rocks, the distinction of Bhipidomella 

 from Schizophoria can be considered to have generic value. There are 

 certainly a large number of shells which can only be assigned to either 

 genus, rather than the other, by unduly weighing one or other of the 

 differences that are to be seen in the typical forms of Schizophoria resupinata 

 and Bhipidomella Michclini. 



