134 PERMIAN FOSSILS. 



Trigonotreta Permiana is of rare occurrence in the shell limestone at Humbleton 

 Quarry and Tunstall Hill/ the only localities known. 



Genus Martinia, M'Coy, 1844. 



Spirifer, Auct. 



Reticularia (included), M'Coy. 



Diagnosis. — " Hinge-line shorter than the width of the shell ; dorsal edges of the 

 cardinal area obtusely rounded ; surface smooth ; spiral appendages small." (M'Coy.^) 



Type, Sjnrifer decora^ Phillips. 



" The short-hinged Spirifers were distinguished long ago by that excellent artist 

 and friend of Mineral Conchology, Mr. W. Martin, and placed by him in a separate 

 division from the long-hinged, ribbed species ; they were afterwards confounded 

 together by the late Mr. Sowerby under the general name of Spirifer, in the ' Mineral 

 Conchology ;' they were then separated again by Professor Phillips, in his admirable 

 ' Geology of Yorkshire,' and form the fourth division of his genus Spirifer ; and more 

 recently Von Buch, in his Memoir on the genus Delthjris, forms of them his second 

 division of the Spiriferidas, but hitherto no author has named, or fully characterised, 

 this most natural genus."^ 



This genus seems to unite Trigonotreta^\\h Atrypa or Athyris. It has the area and 

 fissure of the former, combined with the outline of the latter ; but Atrypa and Athyris 

 also differ from Martinia in being foraminated. 



The histology of the present genus is somewhat variable. In the typical forms the 

 shell is fibrous and fi.nely punctated ; in certain of those forming M'Coy's genus 

 Reticularia the punctures are large, and the fibres appear to be coarse ; and in one of 

 the species hereafter noticed, but in which punctures have not yet been discovered, the 

 fibres appear to have a very coarse character. 



Martinia Clannyana,* Kitiy. Plate X, figs. 11, 12, 13. 



Martinia Clannyana, King. Catalogue, p. 8, 1848. 



Diagnosis. — " A minute species ; as wide as long ; nearly smooth : front slightly 

 emarginate : deltidial valve very convex, with a slight mesial furrow : ventral valve 

 nearly flat : area equilateral : deltidium a little narrower than the area." (King.)" 



^ Through an oversight, the locality " Tynemouth" was given in my ' Catalogue' instead of Tunstall Hill. 



2 Synopsis of the Characters of the Carboniferous Fossils of Ireland, p. 139. 



'^ Loc. cit. 



* Named after the late Dr. WiUiam Reid Clanny, who published in the ' Annals of Philosophy,' vol. vi, 

 a paper entitled ' An Account of the Sunderland Limestone Formation,' and containing the earliest notice 

 of a fish found in the English Permian rocks. 



^ Catalogue, p. 8. 



