166 DR G. W. LEE ON 



than is usually admitted, having, according to him, made its first appearance in 

 Devonian times.* 



Orthid^e. 



Genus Rhipidomella Oehlert. 



Rhipidomella michelini (L'Eveille). (PL I. fig. 16.) 

 Davidson, loc. cit., pi. xxx. figs. 6-8. 



So far as external characters may be trusted, the numerous specimens which I refer 

 to Rhipidomella michelini are undistinguishable from the west of Europe form. 



Genus Schizophoria King. 



Schizophoria aff. resupinata (Martin). (PI. I. fig. 17-1 7 a.) 



Compare Davidson, loc. cit., pi. xxx. fig. 1. 



A single pedicle-valve, globose and very transverse, with a shallow mesial sulcus, 

 has the general appearance of Schizophoria resupinata, from which it differs in the 

 nature of its ornamentation. The ribs are stronger and separated by wider sulci than 

 in the British form ; near the margin the sulci are as broad as the ribs separating 

 them. The shell is very thick. The pores and the pits corresponding to the spine-bases 

 are disposed as in Schizophoria resupinata. 



Schizophoria sp. (PI. II. figs. 24-24c.) 



This species is represented by a complete specimen measuring : — 



Length . . . . .11 mm. 



Width . . . . . 13 „ 



Depth . . . . . 5 ,, 



and by two isolated valves. The ribbing is very fine, and the valves are non-sinuate 

 and much depressed ; the cardinal area is short and low. The shell is very thin. 



A puzzling feature exhibited by the brachial valve after decortication is the hexa- 

 plicate appearance of the muscular impression ; it may be, as suggested by my 

 colleague Dr Ivor Thomas, who kindly looked at the specimen, that the posterior con- 

 centric division is but the termination of unusual accretion of material below or about 

 the cardinal process. The cast of the brachial valve of Orthis pulvinata Salter, shows 

 ■ in identical feature, due, as explained by Salter, to the impression of the " hinge-teeth " 

 and of the cardinal process, the three happening to be of the same length in this species ; 



* E. Schellwien, loc. cit., p. 17 ; and " Beitrage zur Systematik der Strophomeniden des Oberen Palaeozoicum," 

 Neues Jahrbuch, Bd. i., 1900, p. 5. 



