106 



MOLLUSCA. 



[Mactracea. 



4. Ampiiidesma tbuncata, pi. XLII, f. 4. 



Liquid truncate, First Ed., pi. 14, f. 4; Amphidesma trun- 

 catum, Fleming, p. 431. 



Shell subovate, rather convex, oblique ; anterior side pro- 

 duced ; posterior side rather straight, and subtruncated below ; 

 with a flexure, emanating from the umbo, and terminating on 

 the margin ; umbones small, nearly central, and slightly in- 

 flected, beneath them a lanceolate cavity or lunule, covered 

 with transverse, nearly obsolete stria?, and wrinkles ; surface 

 white, smooth, and glossy ; hinge with a double primary tooth 

 in each valve, and a small tooth-like knob in the left valve, 

 locking into a cavity for its reception in (he opposite one; in- 

 side smooth, glossy, and white ; each valve provided with two 

 large muscular impressions ; margins rather thick, for the size 

 of the shell. Length three-eighths of an inch ; breadth half 

 an inch. 



Found at Greenock, by Stewart Ker, Esq., and is in the 

 cabinet of Lady Jardine. 



Genus 32. — Ligula Montagu. 



Shell inequival've, inequilateral, transversely elongated ; with 

 a large, broad, strong, transverse, spoon-like tooth in each valve, 

 projecting inwards, each furnished with a pit for the insertion of 

 the cartilage; right valve furnished with a pretty large, elevated, 

 erect, compressed tooth, situated close below the beak, fitting 

 into a hiatus for its reception, which reaches to the beak, in 

 the opposite valve; and in some species a minute tooth; exter- 

 nal surface with a very thin, membranaceous epidermis ; two 

 muscular impressions in each valve, situate very close to the 

 extreme sides of the valves, the posterior ones double, and ex- 

 tending to nearly the umbones; pallia! impression with a rather 

 large, transverse sinus, situated posteriorly. 



1. Ligula pr/etenuis, pi. XLII, f. I. 



Ligula prcetenuis, First Ed., pi. 14, f . 1 ; Anatina prcete- 

 nuis, Turton, Biv., p. 48, pi. 4, f. 4 ; Amphidesma prcetenue, 

 Fleming, p. 432; Bontcea prcetenuis, Leach, MSS., p. 6; Mya 

 pr&tenuis, Montagu, p. 41, pi. 1, f. 2 ; Donovan, V, pi. 178. 



Shell oval, thin, very brittle, compressed, and semipellucid ; 

 umbones nearly central, very small ; beaks rather acute, and 

 inflected ; posterior side rounded ; anterior side somewhat acu- 

 minated, and obliquely subtruncaled, at which extremity the 

 valves are a little open ; surface cream-white, transversely 

 wrinkled, with extremely fine, nearly obsolete, concentric striae, 

 covered with an extremely thin, cream-coloured, somewhat 

 pilous epidermis ; hinge with a broad, horizontal, internally 

 projecting, hollow tooth in each valve ; inside white. Length 

 about half an inch ; breadth somewhat more than an inch. 



This rare British shell has been found at Poole, and other 

 places on the Dorsetshire coast ; the south coast of Devon ; 

 Frith of Forth ; and Portmarnock, Ireland. 



Genus 33 Tellimya Brown. 



Shell equivalve, inequilateral, suborbicular, or transversely 

 elongated, close all round; left valve destitute of cardinal teeth, 

 but provided with a pretty large hiatus, and two projecting 

 lateral teeth, each having a groove in its centre ; sometimes 

 with one or two rather long teeth on the right side; right valve 



with two recurved, prominent teeth, which occupy the vacant 

 space below the umbo in the opposite valve ; muscular impres- 

 sions large and distinct ; pallial impression entire. 



Section I. — Shells orbicular. 



1. Tellimya suborbicularis, pi. XLII, f. 14, 15. 

 Tellimya subovbicidaris, First Ed., pi. 14, f. 14, 15 ; Mya 



suborbicularis, Montagu, p. 39, pi. 26, f. 6; Maton and Rackett, 

 VIII, p. 41 ; Kellia suborbicularis, Turton, Biv., p. 57, pi. 

 11, f. 5, 6; Fleming, p. 430; Forbes, p. 49; Bomia injlata, 

 Phillipi. 



Shell suborbicular, very convex, thin, subpellucid ; umbones 

 obtuse, nearly central, slightly inflected ; sides almost equal, 

 rounded ; basal margin nearly parallel ; surface of a yellowish- 

 white colour ; somewhat glossy, with faint concentric stria? ; 

 hinge with a single tooth in one valve, immediately under the 

 beak, locking into a double incurved one in the opposite valve, 

 with a somewhat laminated tooth behind the umbo in each 

 valve ; inside glossy, white. Length three-eighths of an inch ; 

 breadth half an inch. 



Some specimens exhibit a fine pearlaceous lustre, when de- 

 prived of the epidermis. 



Inhabits the Frith of Forth, Plymouth, Salcomb Bay, and 

 coasts of the Isle of Man. It is a borer, and penetrates the 

 hardest limestone ; Forbes found it in the cavities of dead 

 bivalves. 



2. Tellimya lactea, pi. XLII, f. 10, 11. 



Tellimya lactea, First Ed., pi. 14, f. 10, 11 ; Brown, Conch. 

 Text Book, p. 138, pi. 17, f. 14. 



Shell nearly orbicular, inflated, thin, pellucid, and glossy 

 white ; one valve with two teeth, locking into a triangular void 

 in the opposite valve, with transverse lamina? on each side ; left 

 valve with a single, recurved, cardinal tooth, and a central, tri- 

 angular, lamellated tooth ; and one remote, lateral tooth only. 

 About a quarter of an inch in diameter. 



Found on the Devonshire coast, by Dr. Leach. 



3. Tellimya tenuis, pi. XLII, f. 12, 13. 

 Tellimya tenuis, First Ed., pi. 14, f. 12, 13. 



Shell orbicular, smooth, glossy, snow-white, with fine, irregu- 

 lar, concentric stria?, much inflated ; umbones rather produced, 

 and much turned to one side ; left valve destitute of cardinal 

 teeth, but provided with two large lateral teeth ; right valve 

 with two incurved, cardinal teeth, and a lateral one ; inside 

 white, and when viewed through a strong lens, has a shagreen- 

 like appearance. Diameter three-eighths of an inch. 



Found at Newbigging, Northumberland, by W. C. Trevelyan, 

 Esq., and is in the cabinet at Wallington. 



Section II. — Shells transversely ovate. 



4. Tellimya elliptica, pi. XLII, f. 16, 17. 

 Tellimya elliptica, First Ed., pi. 14, f. 16, 17; Mya ferrugi- 



nosa, Montagu, Sup., p. 22 and 166, pi. 26, f . 2 ; Montacuta 

 Jemtginosa, Turton, Biv., p. 60. 



Shell transversely subovate, moderately convex, white, with 

 obsolete, concentric wrinkles, and sometimes blotched with rust- 

 coloured spots; umbones obtuse, situate nearest one side; basal 

 margin nearly parallel; hinge with two projecting teeth, one of 

 which is erect, the other slopes inwards and downwards, these 



