:»* 



MOLLUSCA. 



[CONCHACEA. 



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 ; pallia] 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 Lucinae 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. 54 I ; 

 Fleming, p. 441 ; Forbes, p. 47 ; Tellina radula, Montagu, p. 

 68, pi. 2, f. 1, 2; Maton and Uackctt, p. 54; Venus borcalis, 

 Donovan, IV, pi. 130. 



Shell suborbicular, convex ; umbo central, small, slightly pro- 

 duced, blunt, a little inflected; lunule oblong, cordiform, much 



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 verv 

 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 rotundata, First Ed., pi. 16, f . 1 1 ; Lucina rotundata, 

 Turton, Biv., p. 114, pi. 7, f. 3 ; Tellina rotundata, Montagu, 

 p. 71, pi. 2, f. 3; Maton and Rackett, p. 56; Brown, Wemerian 

 Mem., II, p. 508; Psammobia 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. 1 7, 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, Falmouth, 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 slight ly inflected; destitute of a lunule; 

 surface of a pale, dull fawn-colour, or white, with numerous, 

 fine, close-set, irregular strisc, 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 ate sometimes glossy externally. The variety, 

 fig. 1, is from Belfast Lough, Ireland. 



Found on most of the British and Irish coasts. 



