R. Etheridge, Jun. — On Carboniferous MoUusca. 155 



reflected lip in B. decussatus. The cross strige characteristic of the 

 species have almost entirely disappeared, but still remain here and 

 there. The reflected lip, it will be seen, after assisting to form the 

 lateral prolongations or wings over the umbilicus, which is nearly 

 concealed by them, proceeds down each side the shell, forming two 

 advanced points, leaving between a deep rounded concavity over 

 the dorsal keel. Immediately over that part of the keel which it 

 covers, this reflected lip is flattened, but between this and the two 

 lateral prolongations are two hollows, one on each side, giving to 

 the median line of the shell a strongly marked outline. The 

 nearest approach to this that I have yet met with is Woodward's 

 figure of B. hicarenus, Lev,,* although there is a strongly reflected 

 lip shown in the previously referred to figure of MM. D'Archiac 

 and de Verneuil of B. elegans, D'Orb. In his " Animaux Fossiles " 

 Prof, de Koninck regarded the last named as a synonym of B. 

 decussatus, Flem., but in his later work on the Carboniferous Fossils 

 of Carinthia he appears to regard them as distinct. How far the 

 highly reflected lip in the present case will influence its specific 

 identity, I am not prepared to say : it may be only the result of age. 

 Log. and Horizon. — Linn Quarry, about four miles north of Dun- 

 fermline, Fife, in shale connected with one of the Lower Limestones 

 of the L. Carb. Limestone Group. For the specimens, I am again in- 

 debted to the kindness of Mr. J. Bennie, who collected them. 



B. decussatus, var. nndatus, var. no v. Plate VI. Figs. 9 and 10. 



The shell to which I have given this varietal name occurs with 

 other marine fossils in a bed of shale in the Wardie Shale Series of 

 the Lower Carboniferous Eocks near Edinburgh, and although I was 

 at one time inclined to regard it as an undescribed form, I now 

 think it will be better to look upon it as a variety only of B. decus- 

 satus, possessing, however, characters of too marked a nature to be 

 altogether passed over. In the young state, the transverse decus- 

 sating striae, and the small nodes formed by their contact with the 

 longitudinal strias, are visible ; but as the shell grew, the former dis- 

 appeared, or partially disappeared, and a number of transverse broad 

 obtusely rounded inequidistant wave-like fluctuations or corrugations 

 appear. The longitudinal strise are sometimes irregular in their 

 course, and vary in size on the same specimen, a character ascribed 

 by Portlock to his B. interlineatus, which is probably a variety of 

 B. decussatus. The keel becomes flattened with age, but retains its 

 transverse striae, in places assuming the form of scale-like laminae, 

 concave backwards. 



EXPLANATION OF PLATE VI. 



Fig. 1 and \a. Vincularia Benniei, E. Etheridge, jun. From sliale over No. 2 Lime- 

 stone (L. Carb. Limestone Group), Carlops. 



,, 2. Aviculopecten ? sublobatus, Phill. From Carboniferous Limestone, Longnor, 

 Derbyshire. Coll. M.P.G. Eight valve, natural size. 



„ 3. The same. Eight valve, natural size, with six simple colour bands ; a portion 

 only of the ear is visible, 



1 Man. Mollusca, 2nd ed. 1868, t. U, f. 27. 



