Mr. R. Etheridge onGarhomferons Lamellibranchiaia, 103 



Craigleith Quany, near Edinburgh, Cement-stone gi'oup, of 

 the Lower Carboniferous series ; the individuals much crushed, 

 and usually more or less pyritized. Shale containing marine 

 fossils {Orthoceras^ Discina^ Bellerophon^ &c.), Water of Leith, 

 at Woodhall, near Juniper Green, about five miles west of Edin- 

 burgh ; also in the Cement-stone group (fig. 10) . Collection 

 of the Geol. Survey, Scotland; collected by Mr. J. Bennie. 

 Brown sandstone of Knockhill Quarry, Strathkinness, St. 

 Andrews, Cement-stone group ; cabinet of Dr. Traquair 

 (fig. 9). 



Genus Myalina, De Koninck, 1844 

 (Descr. Anim. loss. Terr. Carb. Belgique, p. 125). 



Myalina ? trigonalis, sp. nov. PI. IV. fig. 8. 



Sj). char. Transversely trigonal, diagonally gibbous ; an- 

 terior side short and rounded ; posterior side obtusely rounded 

 ventrally, flat, wing- like, and slightly falcate dorsally. Ven- 

 tral margin convex ; byssal sinus slight. Hinge-line as long- 

 as the shell, thickened ; beaks convex, anterior, but not ter- 

 minal. Shell ornamented with regular, broad, obtusely 

 rounded or almost flat concentric plaits or wrinkles, which 

 become finer and closer on the anterior side, and apparently 

 quite flat on the posterior wing. 



Ohs. I have not been able to ascertain the internal hinge- 

 characters of this shell, and am in doubt whether it should be 

 referred to Avicula, Pterinea, or Myalina. Its reference to 

 the latter, however, is borne out by the somewhat thickened 

 hinge-margin, which is apparent in two specimens. On the 

 other hand, the anterior end is not obsolete in M. ? tngonalisj 

 as it sliould be according to Prof. M'Coy's redefinition of the 

 genus. The chief characters of the species are the almost tri- 

 angular outline, position of the beaks, at less than a third 

 from the anterior end, and the flat, regular, concentric plaits. 



With such forms as Myalina Verneutlit, M^Coy*, and Af. 

 crassa, Flem.f, a comparison is unnecessary. From M. Foy~ 

 nesiana^ Baily j, it may be distinguished by the more produced 

 posterior wing and less obliquely truncated posterior end, &c. 

 Although resembling some of the Pteronites in form, the ra- 

 diating ribs or striae, usually found in species of that genus, 

 are here totally wanting. M. trigonalis appears to be a very 

 close ally of Pterinealinformis^ M'Coy§, but has not tlie very 



* Avicula, Syn. Carb. Foss. 1844, p. 85, t. 13. f. 19. 

 t Etheridge, Ann. & Mag. Nat. Hist. 1875, xv. p. 427. 

 X Mem. Geol. Survey Ireland, Expl. 142, 1860, p. 13, f. 4. 

 § Avimla, Syu. Carb. Foss. p. 83, t. 13. f. 21. rteruiea?, Brit. Pal. 

 Fo99. p. 479. 



8* 



