THE BRACHIOPODA. 35 



Dimensions. Length, 5 ; breadth, 5 ; depth, 4 lines. Depth 

 of sinus about two lines. 



33. KHYNCHONELLA SUBTETRAHEDRA, Davidson. 



1851. KHYNCH. SUBTETRAHEDRA, Dav., British Brach. Palseont. 

 Soc., plate xvi., figs. 9-12. 



1851 (?). ,, INCONSTANS, Davidson, plate xviii., fig. 4 only. 



This species is variable and rather hard to define. It seems 

 to be rather characteristic of the higher bed of the inferior 

 oolite, the most typical specimens coining from the zone of Cosm 

 Parkinsoni. The species is somewhat wider than long, with a 

 mesial fold not much raised, containing from 6-9 ribs. Dorsal 

 valve moderately convex. I have placed as a synonym of this 

 species the shell figured as " Rhynch. inconstans from the upper 

 beds of the Inferior oolite " (Davidson, plate xviii., fig. 4), but 

 with some uncertainty, as I have not material enough to deter- 

 mine whether this form is merely a variation or not of Rhynch. 

 subtetrahedra. I am also not able to say what the young 

 forms of this species may be, but I think it probable that some 

 of the rather flat small Rhynchonellae may belong to it. I 

 expect, however, that it would be extremely difficult to separate 

 well the young forms of Rhynch. subtetrahedra and Rhynch. gin- 

 gensis, Waagen, though the adult specimens are quite distinct. 



Dimensions. Length, 16; breadth, 19; depth, 12 lines. 



Localities. Near Half-way House and Broadwindsor (Dorset), 

 Stoford (Somerset), also Dundry (Somerset), and Leckhampton 

 Hill (Gloucestershire). 



34. RHYNCHONELLA PLICATELLA, Sow. 



1825. TEREBRATULA PLICATELLA, Sow., Min. Conch., table 503, 



fig. 1. 

 1851. RHYNCIIONELLA PLICATELLA, Dav., Fossil Brach. Palseont. 



Soc., plate xvi., figs. 7 and 8. 

 1877. ,, PLICATELLA, Dav., Proceedings Dorset 



Club, Vol. I., plate iv., figs. 9 and 10. 





