HIXD 
THE MILLSTONE GRIT FAUNA 
31 
On the ears of the left valve the radiating costse are crossed 
by concentric lines of growth which, as they cross them, make the 
cstse imbricate. 
Dimensions. — PI. IV., Fig. 8, a left valve, measures : — 
Anteroposteriorly, 40 mm. 
Dorsoventrally, 38 mm. 
Transversely, 10 mm. 
Localities. — Millstone Grit, Hazel Hill, Glints Quarry. 
Observations. — Some half-dozen good specimens have been 
obtained mostly in the form of casts, but an accurate idea of the surface 
marking can be obtained from squeezes of the external cast. One 
bivalve specimen is fortunately to hand, and this shows the typical 
characters of Limatulina. Meek, Op. supra cit., in describing the right 
valve of A. occidentalis states — " right valve nearly flat and having 
the general outline of the other excepting that its beak is scarcely 
distinct from the cardinal margin." I understand this to mean that 
the umbo of the left valve was raised over that of the right valve, and 
to indicate that the shell is a Limatulina and not Aviculopecten. The 
position of the opposing valves at the umbones is well shown in 
figures 7, 7a, Plate III. 
L. occidentalis is a larger shell than L. scotica, comparatively 
broader and more gibbose. The ornament in L. desquamata and the 
radiating lines are not so reojular. 
L. alternata is much narrower and more convex. 
tellinomorpha transversa sp. nov. 
[Plate v., Fig. 24]. 
Specific Characters. — Shell transverse, tumid, superior and 
inferior borders sub-parallel, very inequilateral. The anterior end, 
short, depressed, narrowed, ellipsoidal. The inferior border almost 
straight, the posterior obliquely truncate, posterior inferior and superior 
angles well marked ; the hinge line almost straight. The umbones 
are small, elongate, tumid and placed at the junction of the anterior 
and middle thirds of the valve. Lunule and escutcheon we]^ 
marked. The latter bounded externally by a rolled margin. The 
dorsal slope is hollow. The rest of the valve tumid. A well-marked 
oblique fold passes from the umbo to the posterior inferior angle. 
