MODIOLA. 93 



1858. Mttiltts ^qualis, F. J. Picfet and E. Renevier. Foss. Terr. Aptien 



(Mater. Pal. Suisse, ser. 1), p. 116, pi. xvi, fig. 2. 



1865. — — H. Coqvand. Mon. Aptien tie I'Espague, ]>. 143. 



1868. — — E. EicJiwald. Letliisa Rossica vol. ii, p. 531. 



1867. — — F. J. Pldet and G. Cam/irhe. Foss. Terr. Cr^'t. Ste, 



Croix (Mater. Pal. Suisse, ser. 4), pp. 496, 507. 



1883. MoDiOLA OBESA, W. Keeping. Foss., &c., Neoc. Upware and Brickhill, 



p. 117, pi. vi, fig. 3. 



? Non 1846. — ^equalis, A. E. lienss. Die Versteiu. tier biihm. Kreitleforniat., 



pt. 2, p. 15, pi. xxxiii, fig. 10. 



— 1866. — — K. A. Zittrl. Die Bivalv. tier Gosaugeb , pt. 2 



(Denksolir. tl. k. Akad. Wissen. Math.-nat. CI. Wien, 

 vol. xxv), p. 80 (p. 4 of reprint), pi. .xi, fig. 4. 



— 1882. — — J. Kienoir. Schrift. tier nat. Gesell. in Danzig, vol. v, 



p. 240. 

 ? — 1885. — — F. Notlhuj. Die Fauna der baltisch. Cenom. (Paloeont. 



Abhandl., vol. ii), p. 24, pi. iv, fig. 1. 



Dei^cription. — Shell ovate-oblong, rather short, rounded at the ends, convex, 

 compressed posteriorly. Dorsal and ventral margins usually nearly' parallel. 

 Umbones obtuse, not terminal. Carina absent or very indistinct ; greatest con- 

 vexity of valve between the umbo and the postero-ventral extremity. A slight 

 mesial groove produces a small sinus near the middle of the ventral margin. 

 Surface smooth except for the presence of small concentric ridges, which are best 

 marked anteriorly and postero-dorsally. 



Measurements : 



Length 

 Height . 

 Thickness 



(1 — 7) all from the Crackers of Atherfiekl. 



Affi-uitics. — The young forms of M. reversa, Sowerby, are distinguished from 

 this species by the greater obliquity of their ventral margins. M. Fittoni, d'Orbigny,^ 

 appears to differ from M. sequalis in the presence of a distinct carina with radial 

 striae in front of it, and also in its greater length. 



Forbes and Morris considered that M. Archiaei, Leymerie,^ and M. hipartita, 

 Leymerie, non Sowerby, were identical with M. sequalis. Some of our specimens 

 agree very closely with Leymerie's figures of the latter, but with the former the 

 agreement is not quite so satisfactory ; the figures given by d'Orbigny,"^ and by 



1 'Prodr. de Pal.,' vol. ii (1850), p. 81. 



- ' Mem. Soc. gt'ol. France,' vol. v (1842), p. 8, pi. x, fig. 2. 



3 ' Pal. rran9. Terr. Cre't.,' vol. iii (1845), p. 291, pi. cccxliv, figs. 10—12. 



(1) 



(2) 



(3) 



(4) (5) 



(6) 



(7) 



29 



28 



27 



22-5 22 



21 



15 mm 



14-5 



15 



12-5 



12 11-5 



10-5 



9 „ 



15 



15 



14 



11 10 



9-5 



9 „ 



