LAMELLIBRANCHIATA. | UPPER PALAXOZOIC MOLLUSCA. 513 
angle obtuse, angular ; respiratory angle prominent, obtusely rounded, from whence a strong, rounded, diagonal 
ridge extends to the beak; ventral margin very convex a little behind the middle, but with a slight sinus in front 
of the respiratory angle, from whence a shallow depression extends in front of the diagonal ridge to the beak ; 
portion of the ventral margin from the middle to the anterior end less curved than the rest; valves moderately 
tumid, most so about the middle and obliquely from the beak to a little behind the middle of ventral margin; 
posterior slope flattened. Surface nearly smooth, with extremely delicate concentric stric, and a few stronger 
irregular lines of growth. Length six lines, greatest proportional width (at right angles to middle of hinge- 
line) 55, length of anterior end i, length of hinge-line from beak =, from beak to respiratory angle 7, depth 
of both valves *. 
In Prof. Phillips’s figure the little sinus in front of respiratory angle, and corresponding sinus in front of 
the diagonal ridge, are not, I think, sufficiently marked, and the anterior part of the ventral margin is rather 
too convex, diminishing the apparent obliquity. As M. d’Orbigny in his Prodrome, page 133, refers this fossil 
to the genus Cardiomorpha, 1 thought it proper to cut down a part of the hinge-line of one of the valves of the 
University specimen, and had the pleasure of finding the hinge-teeth, and determining the disputed point as 
to the genus. 
Position and Locality—Rare in the carboniferous shale of Glasgow. 
Nucuta Vinti (King Sp.) 
Ref. and Syn. = Leda Vinti King, Perm. Foss. t. 15. f. 21, 22; and Geol. Russ. p. 224. = Nucula speluncaria 
Geinitz. Verst. t. 6. f. 6. 
Desc.—Subclayate ; beaks almost central, obtuse, moderately prominent, and strongly inclined towards the 
posterior side ; anterior side very large, obtuse, semielliptically rounded ; posterior end very abruptly contracted 
by avery deep cordate depression immediately behind the beaks, which passes gradually into the obscurely defined, 
posterior slope; hinge-line and ventral margins slightly converging to the obtusely pointed posterior end, which 
has an obscure, oblique truncation; ventral margin moderately convex in the anterior half, nearly straight in 
the posterior half; valves moderately tumid, most so about the middle. Surface marked with extremely fine 
concentric elevated lines (fifteen in one line at three lines from the beak), slightly irregular in some parts, and 
abruptly ceasing on the posterior third of the valves, which is smooth. Internal casts shew the muscular im- 
pressions and entire pallial scar, and the angulated row of hinge-teeth, of which there are about nine before 
the beak, and six behind it, with a shallow transyerse sulcus extending about one-third the width from the 
beak to the ventral margin. Length seven lines, proportional length of anterior end ;%, of posterior end +, 
greatest width from beak to ventral margin =, depth of both valves =. 
This is a well-marked species, remarkable for the great size of its anterior end, and the backward direction 
of its beaks, &c. The entire pallial scar renders Prof. King’s reference of the fossil to Zeda incorrect. 
Position and Locality —Not very uncommon in the lowest beds of the Permian magnesian limestone of 
Humbleton. 
7th Family. UNIONIDA. 
Shell inequilateral, very variable in shape and thickness, pearly inside ; beaks usually eroded; margin closed 
or slightly gaping at each end; hinge with or without teeth; ligament external; usually two buccal and one 
anal muscular impressions in each valve ; often a thick periostraca. Animal large ; mantle open, or defining two 
short tubes at the anal end ; foot short and compressed, or very long and terminating in a button-like swelling 
Live in fresh water. 
The family contains numerous genera: Ist, Unio; 2nd, Monocondylea; 3rd, Anodon; 4th, Mycetopus ; 
5th, Castalia; 6th, Iridina; 7th? Carbonicola, &e. 
