564 ME. E. E. L. DIXON AND DR. A. VAUGHAX ON [Nov. I9I I, 



In Northumberland it has been found by Mr. Stanley Smith at 

 the level of the Acre Limestone (probably of D 2 _ 3 age) ; it is there 

 associated with a brachiopod fauna similar to that of Wick and 

 with corals of Oystermouth facies. 



The form from the Curkeen Limestone of County Dublin also 

 occurs at approximately the same level. 



Martinia. 



Martinia glabra (Mart.), varietal form. 



Compare 31. glabra, rnut. P., ' Lougbsbinny Paper ' p. 468 & pi. 1, fig. 8. 



This variety differs from Martin's type in its more equidimensional 

 form and in the more flattened brachial valve. The cast of a 

 pedicle-valve shows the absence of dental plates, and the presence 

 of strong ridges which indicate deep furrows in the interior of the 

 valve — characters which are distinctive of the genus, and are equally 

 well exhibited in M. oralis (Phill.). 



Compared with the later mutation from P of Loughshinny, the 

 muscular scars are very indistinct, w r hereas they are deeply 

 impressed in the Loughshinny form. 



This variety occurs throughout the Oystermouth Series (D 2 _ 3 ) ; 

 it is rare immediately above the massive limestone of North Colts 

 Hill Quarry, abundant in Oystermouth Quarry, and rare again in 

 the Bishopston cutting. 



ATHYRIDS. 

 Athyris. 



Athyris (Cliothyris) globularis (Phill.). (PI. XLI, fig. 8 a.) 



The holotype of Phillips's species is preserved at the British 

 Museum (Natural History) in the Gilbertson Collection ; it bears 

 clear indication of the former presence of fringed expansions in 

 the fine imprints which they have marked upon the valve. Hence 

 this species may be regarded as a dwarf and late representative of 

 the gens of A. glabristria, with which it agrees precisely in form 

 and in the strongly developed beak. 



The Oystermouth specimens only differ from Phillips's type of 

 A. globularis in the preservation of portions of the actual fringes. 

 These expansions are very close-set, and the 'fringe' starts 

 immediately at the suture-line with the valve. 



Specimens are common at one level in D 2 _ 3 of Oystermouth 

 Quarry, and the species is widely spread at the top of the lime- 

 stone-massif in the Midlands and South Yorkshire. 



Comparison with Athyris (Cliotliyris) roissyi (L'Eveille), 

 Yaughan (figured in this paper, PI. XLI, fig. 86). — The Bristol species 

 is abundant in Km and persists into Z. It differs from A. globularis 

 in its non-tranaverse form, in the upright and small beak, the 

 well-spaced principal expansions, and the existence of a narrow 

 unfringed basal portion at the line of attachment of each expansion. 



