396 Mr. Gwyn Jeffreys on Dredging among the Hebrides. 
Description of a new species of Montacuta. 
Monvracuta TUMIDULA*, Jeffreys. 
Suexi rhomboideo-oval, rather gibbous, thin, semitransparent, 
glossy, and prismatic: sculpture, numerous and _ close-set 
delicate, microscopical concentric striz: colour yellowish: 
epidermis fine and silky: margins, on the posterior side 
extremely short and sloping downwards, without any of the 
angularity which characterizes M. bidentata ; in front gently 
curved; on the anterior side considerably expanding and 
rounded ; on the back rising towards the anterior end: beaks 
small, calyciform, blunt and prominent, incurved, but not 
having any indentation below them; they are placed close to the 
posterior side, which is the shortest and not one-sixth the size 
of the anterior side: hinge-line rectangular, occupying about 
one-third of the circumference: cartilage as in M. bidentata : 
hinge-plate narrow and strong, thicker in the middle, not ex- 
cavated so deeply as in the last-named species, and scarcely at 
all in the right valve: teeth, in the right valve short, trian- 
gular, slightly inclming inwards, not widely separated; in the 
left valve long, erect, laminar, and parallel with the hinge- 
line; the anterior teeth are the largest in both valves: inside 
iridescent and polished, very finely marked (more distinctly 
on the anterior side) with slight lines which radiate from the 
beaks: scars irregularly oblong, conspicuous. L. 0:075. 
BrOu:. 
Hasirat. Muddy ground in the Minch off the north-west 
coast of Ross-shire, in 50-60 fathoms. I there found only a 
single dead specimen ; but twenty years ago I dredged another 
in Skye, which I deferred noticing until I was quite satisfied of 
its differing from M. bidentata. [Since this Report was pre- 
sented, Mr. Dawson has found two more specimens in some 
of the ‘dredge d sand which I had sent him.] Among the shells 
procured by Professor Lilljeborg in Bohuslan, on the south coast 
of Sweden, I observed two or three specimens of the present 
species, one of which he kindly gave me. 
This shell is smaller than MM. bidentata; it may also be dis- 
tinguished from that species by its narrower shape, being con- 
vex instead of compressed, having a glossy surface, and by the 
posterior side being extremely small, with almost a perpendicular 
truncation. That side in M. bdidentata is invariably squarish, 
and more or less angulated. The teeth in the right valve of 
M. tumidula are much smaller, and less widely separated by the 
* Somewhat swollen. 
