494 BRITISH PALAZOZOIC FOSSILS. [LAMELLIBRANCHIATA, 
Genus. ANODONTOPSIS. See Page 270. 
ANODONTOPSIS? PRISTINA (MZ. V. K. Sp.) 
Ref. and Syn. = Amphidesma pristina M. V. K. Geol. Russ. t. 20. f. 5. 
Dese.—Rounded, obscurely rhombic ; beaks moderate or small, obtuse, prominent, submedian ; anterior 
side from beak to opposite point of ventral margin almost semicircularly arched; posterior end broad, very 
obscurely subtruncate, slightly convex from the respiratory angle to the anal angle, where it forms an obtuse 
junction with the hinge-line; ventral margin very regularly convex, most so in the middle; valves gently and 
evenly convex, most so about the middle, from whence the valves arch gradually in all directions ; the posterior 
slope only defined at the anal angle near the beak, where a small portion of it is abruptly compressed. Surface 
nearly smooth, with very faint, obtuse, concentric lines. Internal casts shew the oval muscular impressions joined 
by the simple pallial scar, the anterior one having a faint sulcus (from a ridge) behind it; also the slender 
anterior and posterior lateral teeth of the genus. Length one inch three lines, proportional width from beak to 
ventral margin ;3, length of anterior side about ;;, length of hinge-line about =, from beak to undefined respi- 
ratory angle ~~, depth of one valve ,;;. 
I put a note of interrogation to the genus because I have not seen the cardinal tooth ; the two lateral teeth, 
however, and other internal characters agree well with the genus, and prevent the fossil being referred to 
Myophoria. ‘The figure in the Geology of Russia has the posterior side rather too much narrowed and elliptically 
rounded ; it should rise a little higher, where however the abrupt compression of that part of the posterior slope 
only is well shewn. 
Position and Locality.—Rare in the dark carboniferous limestone of Lowick, Northumberland. 
Genus. MYOPHORIA (Bronn, Leth. 1825). 
Syn. = Schizodus King < Awvinus Sow. 
Gen. Char.—Equivalve, compressed ; beaks submedian, small, prominent, incurved towards the anterior 
or posterior side; anterior side broadly-rounded, sharp-edged (no lunette); posterior end narrowed, obliquely 
truncated, with a distinct flattened posterior slope; hinge-line forming an obtuse angle at the beak, rounded to- 
wards the anterior, and sloping obliquely to the posterior end; cardinal teeth small, that of the left valve largest, 
and cleft or bifid at its edge, and received between the two teeth of the right valve: one long, smooth, internal 
ridge extends from the base of the anterior tooth in each valve, diverging from the beaks at an acute angle with 
the curved anterior dorsal margin (two almost imperceptible projections in the left valve, one on each side of 
the bifid tooth, are counted as teeth by Professor King); ligament external on the sharp margin of the long 
posterior slope ; adductor impressions two in each valve, small, pyriform, each surmounted by a small accessory 
one, connected by an entire pallial scar. 
From the examination which I have been able to make in the Cambridge collection of a number of 
specimens of various species of MZyophoria, from the Muschelkalk, I have satisfied myself of the perfect identity 
in generic character between them and the British magnesian limestone types named Schizodus by King. 
The characters of the last-named genus were communicated to M. de Verneuil, and by him published in the 
Geology of Russia, but at the same time he pointed out the resemblance to one of the valves of Myophoria, as 
figured by Goldfuss and Bronn. Only knowing the figure of one valve he stated he could not complete the 
comparison; but, as aboye mentioned, I have completely ascertained their identity from the examination of the 
objects themselves. In the British species the anterior teeth are less developed than in the more common of 
Muschelkallk ones. The inclination of the beaks is not invariably to the anterior side, they sometimes lean 
slightly backwards. Professor King has given reasons, in his volume on the Permian Fossils of England, for 
confining the name Awinus to the London clay forms, congeneric with A. angulatus, and not applying it to the 
Permian types, for which and their carboniferous allies he proposes the name Schizodus, which must now give 
