290 MALACOZOA. TROPIOPODA. LAMELLIBRANCHIATA. 



bifid tooth, in the other two small teeth and a large triangu- 

 lar depression ; the inner surface glossy, with the muscular 

 impression suhoval, large, and .rather deep ; the ventral mar- 

 gin with about thirty teeth. Length about two-twelfths, 

 height a little more. 



Found by me among shell sand, gathered in the Bay of 

 Cniden, by Mr. Alex. Murray, in November, 1842. 



Mactr a triangularis. Mont. Test. Brit. 99. PL 3. f. 5. — Goodallia 

 triangularis. Turt. Brit. Biv. 77. PI. 6. f. 14. — Goodallia triangu- 

 laris. Flem. Brit. Anim. 429. 



2. Goodallia m'mutissima. Ede7itulate Goodallia. 



Shell trigonal, thick, opaque, smooth, with some faint con- 

 centric strite, dull white, with little gloss ; the umbones very 

 prominent ; in one valve a single large bifid tooth, in the 

 other two small teeth and a triangular depression ; the lateral 

 teeth thin and simple ; the inner surface glossy, yellowish, 

 with the muscular impressions moderate, and the margin 

 destitute of teeth. Length about two-twelfths, height rather 

 less. 



Found among shell sand, from the Bay of Cruden, sent by 

 Mr. Alex. Murray, in November, 1842. 



Mactra minutissima. Mont. Test. Brit. Suppl. 37. — Goodallia 

 minutissima. Turt. Brit. Biv. 77. — Goodallia minutissima, Flem. 

 Brit. Anim. 429. 



Genus 3. Lutraria. 



Animal oval or roundish, much compressed. The 

 mantle with the borders thick and simple, united below, 

 posteriorly forming two long, distinct or united tubes. 

 Foot small, compressed. 



Shell oval or roundish, thin, equivalve, inequilateral, 

 concentrically striate, covered with a thin, dense epider- 

 mis, and more or less open at both ends. Hinge strong, 

 the left valve with a small, angularly bent tooth under 

 the umbo, leaving a vacant triangular space, behind it a 

 large oblique triangular fossa for the ligament ; lateral 

 teeth elongated, little elevated, with a shallow groove 

 between them and the margins ; the right valve similar, 

 but with the plicate tooth obsolete, the lateral teeth 

 forming a thickened margin. Internal ligament trigonal, 

 large ; external email, close to the umbones. Muscular 



