MOLLUSCA. 
98 
Genus 20 Myrtea. — Turton. 
Shell subtriangular, equivalve, nearly equilateral; umbones 
almost central, with a deep, lanceolate lunule beneath them ; 
hinge with a single, central, primary tooth, and a lateral tooth 
on each side, in the left valve, and two cardinal and two slightly 
defined lateral teeth in the right valve ; muscular impressions 
reniform, and shallow ; pallial impression entire ; ligament 
external. 
1. Myrtea spinifera, pi. XXXVI, f. 15, 16, and pi. 
XXXIX, f. 14, 15. 
Ortygia spinifera, First Ed., pi. 20, f. 15, 16 ; Venus spini- 
fera, Montagu, p. 577, pi. 17, f. 1 ; Maton and Rackett, p. 78 ; 
Fleming, p. 443; Myrtea spinifera, Turton, Biv., p. 133. 
Shell somewhat subtriangular, subcompressed ; umbones 
small, acute, and slightly inflected ; posterior or cartilage side 
nearly parallel ; anterior side rather concave ; surface with 
many fine, concentric, sharp, almost equidistant, elevated, 
slightly reflected, laminar ridges, which on the margin of the 
cartilage side become confluent, in pairs, and project in the 
form of a series of short, obtuse spines; between these two 
ridges of spines there is an elongated, subulate, deep, obliquely 
striated cavity, for the reception of the ligament ; at the termi- 
nation of these ridges of spines, the shell is slightly truncated ; 
the intercostal spaces are finely and very minutely striated 
transversely, which can only be seen by the aid of a lens ; 
inside smooth, yellowish-white; margin somewhat flattened, 
and plain. 
Found at Salcomb Bay, Devonshire ; several parts on the 
Western coasts; and at Portmarnock, Ireland, but is a very 
local and rare species. 
Genus 21. — Lucina. — Bruguiere. 
Shell equivalve, inequilateral, usually orbicular, lenticular, 
and subdepressed ; teeth variable, most commonly two minute, 
cardinal teeth, divergent from the umbo, frequently nearly 
obsolete ; in one valve one lateral tooth on each side of the 
umbo, and two on each side in the other ; the anterior lateral 
ones being situate near to the primary teeth, and the posterior 
immediately behind the ligament; two muscular impressions, 
remote from each other, the anterior one generally extended 
backwards and downwards, in the form of an elongated band ; 
pallial impression destitute of a sinus ; ligament external, elon- 
gated, and partly hidden by the inflected margins of the valves 
when closed, consequently the internal tendinous portion is fre- 
quently sunk into a deep, elongated cavity, situate between the 
teeth and hinge margin. 
The Lucinse inhabit the ocean. Fossil species are numerous, 
and occur in the beds of the Tertiary formation, of which they 
are a characteristic type. 
1. Lucina radula, pi. XXXIX, f. 8, 9. 
Lucina radula. First Ed., pi. 17, f. 8, 9; Lamarck, V, p. 541 ; 
Fleming, p. 441 ; Forbes, p. 47 ; Tellina radula, Montagu, p. 
68, pi. 2, f. 1, 2; Maton and Rackett, p. 54; Venus borealis, 
Donovan, IV, pi. 130. 
Shell suborbicular, convex ; umbo central, small, slightly pro- 
duced, blunt, a little inflected ; lunule oblong, cordiform, much 
[Conchacea. 
depressed; posterior side with a longitudinal flexure, emanating 
behind the umbones, and terminating on the side ; whole 
exterior covered with numerous, fine, distant, elevated, con- 
centric, narrow, laminated ribs, which are sharp on the surface, 
and feel rough to the touch, white, or covered with a very 
thin, yellowish-brown epidermis; inside dull white, except 
betwixt the pallial impression and the margin; sinus narrow, 
obliquing downwards, and nearly parallel with the margin ; 
hinge with two oblique teeth in both valves, one of them a 
little cleft. 
This shell is sometimes elongated in form, as in fig. 9. 
Not uncommon on many of the British and Irish coasts. 
2. Lucina rotundata, pi. XL, f. 11. 
Mysia rotundalti. First Ed., pi. 16, f. 11 ; Lucina rotundata, 
Turton, Biv., p. 1 14, pi. 7, f. 3 ; Tellina rotundata, Montagu, 
p. 71, pi. 2, f. 3; Maton and Rackett, p. 56; Brown, Wernerian 
Mem., II, p. 508 ; Psamrnobia rotundata, Fleming, p. 438. 
Shell thin, orbicular, white, and rather convex; umbones 
small, nearly central, obtuse, and very slightly turned to one 
side; surface moderately glossy, with fine, nearly obsolete, con- 
centric striae ; inside smooth, glossy, white ; two teeth in each 
valve, one of which is cleft, and the other slightly divergent. 
Inhabits the sea at Poole, Dorsetshire ; also the coasts of 
Devon and Wales ; and has been met with on several parts of 
the Irish coast, particularly at Bantry Bay. 
3. Lucina lactea, pi. XXXIX, f. 3. 
Lucina lactea. First Ed., pi. 17, f. 3; Lamarck, V, p. 542; 
Turton, Biv., p. 112, pi. 7, f- 4, 5 ; Tellina lactea, Montagu, p. 
70, pi. 2, f. 4; Loripes lacteus, Leach, MSS., p. 9 ; Fleming, 
p. 430. 
Shell thin, orbicular, equilateral, convex; umbones small, 
nearly central, and slightly inflected anteriorly, with a small 
cordiform lunule under them ; surface white, with fine, con- 
centric, irregular wrinkles, sometimes interspersed with a few 
antiquated ridges ; inside white, moderately glossy ; hinge with 
two small teeth in one valve, and one in the other; a deep 
sulcus, by the side of the teeth in both valves, emanating at 
the umbones, for the reception of the cartilage ; margin below 
the pallial impression shining, slightly and obsoletely striated 
longitudinally. 
Found at Torbay, Falmoutb, Kingsbridge, and Poole. 
4. Lucina undata, pi. XXXIX, f. 1,2. 
Lucina undata. First Ed., pi. 17, f. 1, 2; Lamarck, V, p. 
543; Turton, Biv., p. 115; Forbes, p. 47 ; Venus undata. Pen- 
nant, IV, p. 95, pi. 55, f. 51; Montagu, p. 117; Fleming, p. 
148; Donovan, pi. 121; Maton and Rackett, p. 86; Mysia 
undata, Leach, MSS., p. 9* 
Shell nearly orbicular, thin, flexous ; umbones prominent ; 
beaks rather acute, and slightly inflected; destitute of a lunule; 
surface of a pale, dull fawn-colour, or white, with numerous, 
fine, close-set, irregular striaj, which in some instances run into 
uneven, irregular wrinkles ; hinge strong, with three teeth in 
one valve, and two in the other, the posterior one cleft ; inside 
smooth, glossy ; margin plain, with an acute edge ; the sinus in 
the pallial impression very large, reaching nearly to the middle 
of the valves. 
Young shells aie sometimes glossy externally. The variety, 
fig. 1, is from Belfast Lough, Ireland. 
Found on most of the British and Irish coasts. 
