74 Proceedings of the Royal Physical Society. 



regular serial order, a few other doubtful species liave been 

 referred to. In an interesting and recently published paper, 

 " On the Genera of Gasteropod Mollusca from the Carboniferous 

 Limestone Series of the Central and Western Coalfields of 

 Scotland,"* Mr J. Young mentions the following : — A species 

 of Niso from the Upper Limestone Group of Dairy, the only 

 other reported occurrence of this genus being in the De- 

 vonian rocks of Australia.-|* Siliqttaria again, an Eocene 

 genus, is said to occur in the Upper Limestone shales of 

 Carluke, in the form of a spiral tubular shell, with an open 

 slit along the outer or dorsal margin. 



Before concluding our brief review of the Scotch Carboni- 

 ferous Gasteropoda, a few words must be said about the 

 occurrence of detached opercula. Comparatively few in- 

 stances are on record of these organs in a separate state 

 in our Carboniferous rocks or even found in siho. My friend, 

 Mr James Bennie, was fortunate enough to discover a num- 

 ber of bodies in the siliceous limestone of Dairy quarry, 

 Ayrshire, which are believed to be none other than the 

 opercula of small Gasteropoda. They have, to a certain ex- 

 tent, the appearance of little otoliths, but as one variety was 

 actually observed in the mouth of a small naticiform shell, 

 and their structure otherwise corresponds to that of other 

 opercula, we have regarded them as such.J 



We are confirmed in our opinion by the recently published 

 figures of Professor de Koninck, who gives a series of several 

 species of Naticopsis,^ in every way corresponding to those 

 from Law quarry, but much larger. More than this,De Koninck 

 figures some conical bodies,! I formerly described by him as 

 a genus of Brachiopoda, under the name of Hyi^odema, and 

 before that as a Calceolct. These he now believes to be the 

 operculum of Euompludus. They are pyramidal objects, no 

 two of them alike, one face flat, the other convex, with the 

 summit eccentric and recurved. The inner surface is smooth 



* Trans. Geol. Soc, Edinb. 



t Foss. Pal. Nouv. Galles du Snd., p. 127. 



:J: See Etlieridge, Annals Nat. Hist., 1881, vii., pp. 25-31, t. 2. 



§ Gastoropodes, p. 148, t. 2, figs. 10 and 11, 13 and 14, 23-25. 



Wlbld., t. 9, f. 74-80. 



