Mr. Iv. Etlieridgeo/t Carboniferous LamellihranchiaUi. 433 



tlie bitid tooth of the Permian funn, S. truucafusj King. 

 Perliaps wlieii more i.s known of the dental characters of the 

 vari<jus species constituting the genus Schizodus, we may be 

 able to separate tiicni into two natural groups based on the 

 divided or undivided condition of the large central tooth of the 

 left valve. 



Localities d:c. Ardross Limestone, Ardross, Fifeshire, at 

 the base of the Lower Carboniferous Limestone group ; cabinet 

 of the Rev. T. Brown, who remarks that it is one of the 

 characteristic shells of that bed. Cambo Ness, Kingsbams, 

 Fifeshire, from the M>/alina-heds of the Lower Carboniferous 

 series (Cement-stone gnnip) ; collection of the Geological 

 Survey of Scotland. Water of Leith, at Woodhall, in shale 

 under a bed of sandstone of the Wardie Shale group, Ijower 

 Carboniferous series ; cabinet of Dr. Traquair, and collection 

 of the Geological Survey of Scotland (specimens collected by 

 Mr. J. Bennie). 



The Rev. T. Brown remarks that " the species seems to 

 have belonged properly to the Lower Carboniferous group, 

 rather than to the Mountain Limestone. . . . On passing up 

 into the Mountain Limestone it occurs rather in a straggling 

 condition, and in comparatively scanty numbers." 



In conclusion, I have to cx[)ress my thanks to Dr. Traquair 

 and the Rev. Thomas Brown for so kindly placing specimens 

 at my disposal, and to my colleague Mr. B. N. Peach for the 

 excellent ckawings accompanying these notes. 



DESCRlPTIOiV OF PLATE XX. 



3Ii/alina crassa, Flemiug. 



I'll/. 1. Left valve, uatui-al size. Cults Lime- works, near Pitlessie, Fife. 

 o, hinge-plate with cartilage-fuiTows : 6, scars of origin of the 

 anterior muscular imprtssion divided by the median ridge; c, 

 scar of the insertion of the anterior adductor of the opposite 

 valve ; d, hollow depression or pit in the angle between the 

 hinge-line and the anterior end ; e, groove running from d across 

 the hinge-plate ; /, pallial line, with pita for the muscular fibres 

 of the mantle. 



Fii/. 2. Right valve, natural size. Cults Lime-works. «, b,c, &/ similar 

 to fig. 1 ; (/, raised border bounding the anterior muscular scars. 



Fit/. 3. ? Posterior portion of the sliell, showing a strong muscular scar, 

 natural size. Cults Lime-works. 



Fi(/. 4. Small left valve, e.xterior view, natural size. Woodhall, water of 

 Leitli ; cabinet of Dr. Traquair. 



Fi'i/. 5. Literior view of the same. 



Sihizotlus Salhri, K. Etheridge, jun. 



Fifj. i.\ Right valve, e.vterior view, natural size. Ardro«s«, File; cabinet 

 of the Rev. T. Brown. 



