56 CARBONIFEROUS LAMELLIBRANCHIATA. 



Nou MoDiOLA, Lea, 1853. Journ. Acad. Nat. Sci. Philadelphia, p. 203. 



MxALiNA, Baily, 1860. Mem. Geol. Surv. Ireland, Explan. of Slieet 1-12, p. 13. 

 MoDiOLA, Wardle, 1862. In Sleigh's Ancient History of Leek, p. 285. 

 Non MoDiOLA, Boemer, 1870. Geol. Palaont. Oberschlesien, p. 129, pi. x, fig. 6. 

 Non — B. Ether idg e, jun., 1875. Geo). Mag., dec. 2, vol. ii, p. 241, pi. viii, 



figs. 1 and 2. 

 — pars, de Koninck, 1885. Taune du Calcaire Carbonifere de Beige 



(Ann. Musee E. d'Hist. Nat. Belg.,t. xi), 

 pt. 5, p. 174, &c., pi. xxviii. 



Generic Characters. — Shell oblong, transversely triangular, inequilateral, equi- 

 valve, obliquely swollen, gibbose in front, compressed behind and above. The 

 hinge-line is straight, equalling in length about one half the long diameter of the 

 shell. The umbones are obtuse and not very conspicuous, anterior but never 

 terminal. The hinge is edentulous ; ligament internal, attached to an elongated 

 depression within the margin of each valve. Muscle-impressions obscure, three 

 in each valve, — one anterior, one posterior, and one below the hinge-line. 



Observations. — Many Carboniferous Mytiliform fossils have been grouped 

 under the genus Mocliola. 



Phillips records four distinct forms : — Modiola squamifera, which belongs to 

 a genus in the Area family ; M. lingualis, which for anatomical reasons I have in 

 this work referred to Lithodomus ; M. elongata, which I believe to be the same 

 shell as those which I now refer to Posidoniella, de Koninck ; and M. granulosa, 

 all trace of which has been lost, and from the meagre description and poor 

 drawing it is impossible to identify the shell. 



Sowerby referred one species of Naiadites from the Coal-measures of Coal- 

 brookdale to this genus, to which it is very closely allied in external form. 



Portlock described Modiola Macadamii, three varieties, and M. subparallela 

 from the Carboniferous shales of the north of Ireland. The former group, in 

 which I recognise two distinct forms, I am retaining in this genus ; the latter shell, 

 owing to the discovery of the hinge-plate in a specimen in the Belfast Museum, 

 from Ballycastle, I refer to Anthracomya. 



M'Coy, in addition to species previously described by other authors, described 

 four new forms from Irish Carboniferous beds, — Modiola concinna, M. divisa, 

 M. megaloba, and M. jyatula. Of this M. concinna should be probably referred to 

 Parallelodon. M. divisa also has not the appearance of the genus, and at present 

 I am uncertain as to its real affinity. There is a well-developed posterior ear, a 

 longitudinal groove parallel to the hinge-line, and a curious lineal constriction in 

 the anterior part of the shell (compare Avicula Hendersoni, R. Etheridge, jun., 

 * Quart. Journ. Geol. Soc.,' vol. xxxiv, p. 11, pi. i, fig. 11). I have retained the 

 two species Modiola patula and M. megaloba, though the types of both are absent 

 from the Griffith Collection in the Museum of Science and Art, Dublin. 



