84 MOLLUSCA. 
Inhabits the Mint, near Kendal. 
Rossmassler is wrong in supposing that this variety belongs 
to the form Rotssyt. 
I am indebted to the kindness of Miss Ellen T. Thomson, 
of Stricklandgate, and Thomas Gough, Esq., surgeon, Kendal, 
for specimens and a knowledge of this variety. 
Variety 4. Arcuata, pl. XXX,* f. 3. 
Shell small, subdepressed, thick; hinge line considerably 
arcuated; ligament prominent; basal line greatly curved; car- 
dinal tooth in one valve very large; lateral sinus arcuated, and 
broad as it retires from the cardinal tooth; muscular impressions 
deep. 
Found in the river Derwent, Bassenthwaite, Cumberland, a 
little way below Ouse Bridge. 
Variety 5. Outvacra, pl. XXX,* f. 1. 
Small; substance of the shell thick, rather inflated; hinge line 
nearly parallel; basal line with a flexure, and a very little arcu- 
ated; valves with a slightly hollowed, longitudinal, gradually 
widening furrow, from the umbones to the basal margin; outer 
surface olivaceous, with irregular, transverse furrows; umbones 
much decorticated, which extends nearly to the dorsal extre- 
mity of the valves; inside of a dull flesh-colour, slightly nacred 
towards the dorsal side; teeth small, distinctly tripartite in the 
left valve, and very small and single in the other. 
This very curious variety was discovered by Thomas Glover, 
Esq., of Smedley Hill, in the Leven, a little way below the lake 
of Windermere, Westmoreland. 
Famity IJ.—Arcacka. 
Shells provided with numerous small primary teeth, disposed 
in a straight or interrupted line in each valve. 
Genus 4.—NucuLa.—Lamarck. 
Shell equivalve, inequilateral, transverse, oval, trigonal, or 
oblong; generally covered with an epidermis; hinge linear, 
narrow, divided into two parts by an oblique, produced, nearly 
central pit, which is destined for the reception of the ligament, 
the one anterior and the other posterior; lateral teeth on each 
side numerous, acute, elevated, somewhat recurved, those of 
the opposite valve locking into the intervening spaces; umbones 
contiguous, and not separated by an intervening area; two 
simple muscular impressions; mantle impression destitute of a 
sinus. 
Section I.— Shells oblong-ovate. 
1. Nucuia rostrata, pl. XXXIII, f. 16. 
Nucula rostrata, First Ed., pl. 25, f. 16; Arca rostrata, 
Ency. Meth., pl. 309, f. 7, a, 6; Montagu, Sup., p. 55, pl. 27, 
f.73; Turton, Conch. Dict., p. 11; Ib., Brit. Biv., p. 1783 La- 
marck, VI, pt. Ist, p. 58. 
Shell transversely oblong-ovate, somewhat convex, and rather 
thin; smaller side produced into an arcuated, beak-like form, 
which is provided with three transverse ribs; umbones nearly 
central, approximate, somewhat inclined to the smaller side; 
external surface pale horn-coloured, and a little glossy, with 
strong, regular, undulating, diagonal strie, which make an 
abrupt, angulated turn across the ribs of the beak, terminating 
[ ARCACEA. 
where the ribs of the beak commence; these are crossed by 
extremely minute, irregular, transverse strie, which, however, 
can only be seen by the aid of a strong lens, and appear more 
like the scratches of a file than strie; teeth strong, regular, and 
angulated, those on each side of the hinge pit with their angular 
sides turned towards it; inside very glossy and white. 
not quite half an inch; breadth three-quarters. 
Found off St. Abb’s Head, Frith of Forth, by Captain Las- 
key; and I met with an odd valve at Holy Island. 
2. Nucura minuTa, pl. XXXIII, f. 18. 
Nacula minuta, First Ed., pl. 25, f.18; Turton, Biv. p- 178; 
Arca minuta, Montagu, p. 140; Brown, Wernerian Mem., II, 
p: 512; Arca caudata, Donovan, III, pl. 78; Arca modiolus, 
Walker, p. 23, f. 81. 
Shell transversely oblong-ovate ; anterior side produced into 
an angulated, arcuated beak, which is square at the point; 
Length 
posterior side rounded; umbones small, pointed, and turned 
towards the anterior side, with a small spindle-shaped depres- 
sion under them, reaching to the point of the beak, and being 
indented, gives a reflexed appearance; teeth numerous, sharp, 
and prominent; external surface yellowish or pale olive-green, 
covered with fine, distant, regular, transverse strie, and three 
or four concentric ridges, according to the age of the shell; 
inside smooth, glossy, and of a bluish-white or pale purple; 
Length three-eighths of an inch; breadth some- 
what more than half an inch. 
Found at Sandwich; Tenby; Dublin Bay and Portmarnock, 
Treland; and Frith of Forth, Scotland. 
3. NucvuLa oBionea, pl. XXXIII, f. 17. 
Nucula obsoleta, First Ed., pl. 25, f. 17. 
Shell oblong-ovate ; anterior side produced into a straight, 
but slightly narrowed beak, with two shallow furrows running 
from the apex to the point, which is slightly rounded; posterior 
side rounded; umbones straight, very blunt, and placed near 
the posterior side; exterior surface of a dark olive-green, with 
nearly obsolete, transverse striz ; teeth strong, regular, promi- 
nent, and triangular; cartilage cavity spoon-shaped, and sloping 
downwards; inside smooth, and white; muscular impressions 
margin plain. 
large; a slight groove emanating below the umbones, termi- 
nates on the margin at the beaked side. Length upwards of 
half an inch; breadth upwards of seven-eighths. 
Discovered by Stewart Ker, Esq., at Greenock, and on the 
beach of the opposite shore, where it is not uncommon. 
4, Nucuta TRuNcaTA, pl. XXXIII, f. 19. 
Nucula truncata, First Ed., pl. 25, f. 19. 
Shell ovate, somewhat beaked at its anterior side above, with 
an oblique truncation below the projecting point; umbones 
rather prominent, rounded, and nearly central; outside of a 
dark olive-green, beset with numerous, extremely fine, close, 
considerably undulated, transverse striz, and with exceedingly 
fine, minute, longitudinal striz, which can only be seen by the 
aid of a lens; inside smooth, white; hinge with about thirty 
sharp, elevated, and somewhat imbricated teeth; cartilage socket 
nearly round, sloping downwards, and almost concealed below 
the umbones. Length not quite half an inch; breadth about 
three-quarters. 
Discovered by Stewart Ker, Esq., at Greenock, and near 
Ardencaple, where it is not uncommon. 


