Mr. R. Etlieridi^c v n Carboniferous LameUibranchiaia. 103 



Crai{];lcith Quarry, near Edinburf^h, Ccnient-stonc j^roiip, of 

 the Lower ('arbi)nifiM-oiis series ; the indivichial.s much crushed, 

 and usually more or less pyritizcd. Shale coutaiaini^ marine 

 fossils [Orthoceras.Discinn, Belierophon, &c.). Water of Ix'ith, 

 at \Voodliall,ncar Juniper Green, about five miles west of Edin- 

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

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

 Brown sandstone of Knockhill (,^)uarry, Strathkinness, St. 

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

 (fig. 9). 



Genus Mvalina, De Koninck, 1844 

 (Descr. Anini. Foss. TeiT. Carb. Belgique, p. 125). 



Mt/a!ina? trigonalis, sp. nov. PI. IV. fig. 8. 



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

 terior side sliort and rounded ; posterior side obtusely rounded 

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

 tral margin convex ; byssal sinus slight. Ilinge-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 whetiicr 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 ]\[. ? tn'gonaUs, 

 as it should be according to Prof. iPCoy's redefinition of the 

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

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

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



Witli such forms as Myalina Verneuilii, M'Coy*, and ^f. 

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

 nesiana, Baily f, it may be distinguished by the more produced 

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

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

 diating ribs or strife, usually found in species of tliat genus, 

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

 close ally of Vlerine.a'i informis^ M'Coy§, but has not the very 



• Arictila, Svn. Carb. Foss. 1844, p. 8o, t. 18. f. 10. 

 t Ethoridgp,' Ann. & Macr. Nat. Ilist. 187/5, xv. p. 427. 

 t Mem. Geol. Suncv Ireland, Expl. 142, 18fW, p. 13, f. 4. 

 § Avicida, Syn. Carb. Foss. p. 8.3, t. 13. f. 21. Ptrrwm?, Rrit. Pal. 

 Foss. p. 479. 



8* 



