256 



MALACOZOA. TROPIOPODA. iAMELLlBRANCHlATA. 



declinate; the anterior a little concave near the umbones, 

 where there is a small oblong impression ; a faint sinus from 

 the umbo to the posterior margin ; in the right valve a single 

 entire tooth, with a depression on either side, in the left valve 

 two teeth ; the interior smooth ; the anterior muscular im- 

 pression extremely narrow and elongated, the posterior oblong ; 

 the colour white or yellowish-white ; frequently interrupted 

 crack-like radiating streaks, sometimes tinged red, as if in the 

 substance of the shell. Length eight-twelfths of an inch, 

 height seven-twelfths. 



Single valves found by me on the Belhelvie Sands, in Sep- 

 tember, 1842. 



Very nearly allied to Lucina Radula, from which it differs 

 in having the dorsal line more sloping, the frontal less rounded, 

 the stride more numerous, the anterior muscular impression 

 longer. 



Tellma lactea, Linn. Syst. Nat. 1119. — Telliua lactea. Mont. 

 Test. Brit. 70. PI. 2. f. 4.-lLucina lactea. Turt. Brit. Biv. 1 12.— 

 liucina lactea. Lamk. Syst. v. 542^ Ed. 2. vi. 228, — Lucina lactea. 

 R,isso, Eur. Merid. iv. 343. 



4. Lucina Leucoma. White Lucina. 



Shell roundish, inequilateral, little convex, thin, with nu- 

 merous concentric regular deeply impressed striae, and faint 

 and minute radiating striulas ; the umbones much curved ; the 

 dorsal slope very convex, the anterior deeply concave close to 

 the umbones, afterwards convex, the ventral outline semicir- 

 cular, forming a rounded angle with the frontal ; anterior im- 

 pression cordate, rather deep, striate ; in the right valve a 

 single entire tooth, with a depression before it, in the left, two 

 thick teeth, of which the anterior is cleft ; the intei'ior roughish, 

 smooth and glossy at the margin, the pallial impression in- 

 vaded by a very narrow, straight mark, a deep groove from 

 near the umbo ; the colour dull white. Length of an indivi- 

 dual eight-twelfths, height seven and a-half twelfths. 



The above description from an individual brought up by the 

 lines at Aberdeen, and found by JNIiss Marion JNIacgillivray, 

 in October, 1842. 



Lucina Leucoma. Turt. Brit. Biv. 113. Fl. 7. f. 8. 



Genus 2. Cyprina. 

 Shell equivalve, anisomeral, obliquely cordiform, 

 ovato-orbicular, thick, concentrically costate or striate, 

 with a persistent lamellar epidermis. Umbones promi- 



