The Invertebrate Fauna of the Uitcuhage Series. 85 



by J. Muller,* and united by Holzapfel i under the name Septifer 

 tegulatus, may possibly be identical with Sowerby's M. lanceolatus, 

 according to the view of Prof. Holzapfel and Mr. H. Woods. While 

 the points of difference from M. uitcnhagensis are in the main those 

 noted above in the case of the English shell, the specimens from 

 Aachen dealt with by Prof. Holzapfel appear to be still more strongly 

 distinguished by their frequently curved antero- ventral margin and 

 their well-marked concentric ornament. 



In Mytilus tornacensis d'Archiac,} from the Tourtia of Tournay, 

 the binge-line is relatively longer than in M. uitenhagensis, while the 

 antero-ventral area is not flat and the carina is much less sharp ; there 

 are also markings on the shell at right angles to the lines of growth. 

 A form bearing greater similarity to M. uitenhagensis is Mytilus 

 triangularis J. B6hm, from the Tr/t/oma-sandstone of Lebanon. || 

 This has a similar elongated outline, sharp carinal ridge and 

 flattened antero-ventral area ; but it is apparently well distin- 

 guished by the manner in which the hinge-margin and posterior 

 margin pass imperceptibly by a curve into one another when viewed 

 in profile. In M. triangularis, too, the flank between the carina 

 and the posterior margin is slightly narrower, while Dr. Bohm's 

 figure 116 represents the outline of the carina as somewhat curved. 

 In order to illustrate how great a sameness of characters may 

 persist or recur in mytiloid shells, it is only necessary to refer to 

 such a form as M. aviothensis Buv.H from the Lias of Avioth, Breux. 

 This closely resembles M. triangularis, from the Syrian Cretaceous, 

 in most outward characters, and differs from M. uitenhagensis 

 chiefly in those points which distinguish M. triangularis also, 

 though exhibiting a slight convexity of the antero-ventral area not 

 developed in these Cretaceous forms. 



GENUS MODIOLA Lamarck. 

 MODIOLA BAINI Sharpe. 

 Plate II., figs. 12, 12a. 



1856. Modiola bainii D. Sharpe, Trans. Geol. Soc. Loud., ser. 2, 

 vol. vii., p. 193, pi. xxii., figs. 2, 3. 



Supplementary Descriptive Note. As an addition to Sharpe 's 

 description, it may be noted that the oblique lateral " keel " is only 



* J. Miiller (1), p. 35. f Holzapfel (1), p. 218, Taf. xxv., figs. 1-9. 



J d'Archiac (1), p. 307, pi. xv., fig. 3. J- Bohm (2), p. 218, Taf. vii., fig. 11, 

 1 1 For remarks on the age of this sandstone see Eehbinder (1), p. 87. 

 IT Buvignier (1), p. 24, pi. xvi., figs. 35-37. 



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