Mr. R. Etheridge on Carboniferous Lamellibranchiata. 433 
fo) 
the bifid tooth of the Permian form, S. truncatus, King. 
Perhaps when more is known of the dental characters of the 
various species constituting the genus Schizodus, we may be 
able to separate them into two natural groups based on the 
divided or undivided condition of the large central tooth of the 
left valve. 
Localities &e, 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, Kingsbarns, 
Fifeshire, from the Myalina-beds of the Lower Carboniferous 
series (Cement-stone group); collection of the Geological 
Survey of Scotland. Water of Leith, at Woodhall, in shale 
under a bed of sandstone of the Wardie Shale group, Lower 
Carboniferous series ; cabinet of Dr. Traquair, and collection 
of the Geological Survey of Scotland (specimens collected by 
Mr. J. Bennie). 
The Rey. '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 express 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 drawings accompanying these notes. 
DESCRIPTION OF PLATE XX. 
Myalina crassa, Fleming. 
Fig. 1, Left valve, natural size. Cults Lime-works, near Pitlessie, Fife. 
a, hinge-plate with cartilage-furrows ; 6, scars of origin of the 
anterior muscular impression divided by the median ridge; c, 
sear 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 ; f, pallial line, with pits for the muscular fibres 
of the mantle. 
Fig. 2. Right valve, natural size. Cults Lime-works, a, 6, c, & f similar 
to fig. 1; g, raised border bounding the anterior muscular scars. 
Fig. 8. ? Posterior portion of the shell, showing a strong muscular sear, 
natural size. Cults Lime-works. 
4, Small left valve, exterior view, natural size. Woodhall, water of 
Leith ; cabinet of Dr. Traquair. 
Fig. 5. Interior view of the same. 
Fig. 
Schizodus Saltert, R. Etheridge, jun. 
Fig. 6, Right valve, exterior view, natural size. Ardross, Fife; cabinet 
g; 5 ro ’ ’ } 
of the Rey. T. Brown. 
