430 Ml'. R. Etheridge on Carboniferous Lamellihranchiata. 



posterior adductor-scars with satisfaction. Fig. 3 represents 

 the posterior portion of a shell with a strong muscular scar, 

 which, I think, may be that of .1/. crassa] it was obtained at 

 Pitlessie with many fragments of that species, and from the 

 same block of shale. The margin of the scar is strongly 

 defined ; and there are several pits scattered along it and over 

 the surface of the impression, probably marking the points of 

 attachment of muscular fibres. 



In the water of Leith at Woodhall a bed of dark shale 

 occurs, with a species of ^f^/al(na in abundance, the individuals 

 varying in size from small specimens up to near that of the 

 typical M. crassa. Except that the shell of the Woodhali 

 form is thinner, and, as before stated, smaller, I cannot distin- 

 guish one from the other. 



Localities dx. Cults Lime-works, near Pitlessie, Fife, " in a 

 bed of shale over the Mountain Limestone ;" Fleming Collec- 

 tion, Edinburgh Museum of Science and Art, and collection of 

 the Geological Survey of Scotland : collected by Messrs. Bennie 

 and !Macconochie. Lugton Water, near Lugton Inn, near Dun- 

 lop, Ayrshire, in shale in connexion with the lowest limestone 

 of the Lower Carboniferous Limestone group ; collection of 

 the Geological Survey of Scotland, collected by Mr. A. Mac- 

 conochie. Woodhali, water of Leith, in shale of the Wardie 

 Shale series. Lower Carboniferous series ; cabinet of Dr. 

 Traquair, and collection of the Geological Survey of Scotland : 

 collected by Mr. J. Bennie. Messrs. Armstrong and Young 

 record M. crassa from shale below the main limestone at 

 Rough wood, and from clay-ironstone shale at Corrieburn*. 



In the article on " Fife and Kinross," in the ' New Statis- 

 tical Account of Scotland 'f, is the following reference to the 

 bed of shale at Cults Lime-works : — " One of the beds of shale 

 which overlies the main lime is composed entirely of shells of 

 the genus Mytilus, the prevailing species being the M. crassus. 

 These shells appear as fresh and entire as if they were still 

 reposing on the mud bed of the primitive ocean in which they 

 were produced. Not only are the external figure and internal 

 structure preserved, but even the colour and original shelly 

 matter seems to have sustained but little alteration." 



Many of the valves of M. crassa from Cults have attached 

 to them a large Spirorbis, described by Fleming in his 

 memoir on the Testaceous Annelides as S. ambiguiis. Mr. 

 Bennie has met with a similar form at Roscobie, Fife. 



* Trans. Geol. Soc. Cllaspow. iii. Siipp. p. 52. 

 t Vol. V. p. 561). 



