MALACOZOA. TROPIOPODA. LAMELLIBRANCHIATA. 303 



Found by Miss Anne Macgillivray, in September, 1842, in 

 shell sand, from near the mouth of the Dee. 



Montacuta oblouga, Turt. Brit. Biv. 61. PI. 11. f. 11, 12. 

 3. Montacuta glabra. Smooth Montacuta. 



Shell ovato-oblong, subelliptical, very thin, somewhat pel- 

 lucid, very inequilateral, nearly equally rounded at both ends, 

 convex, delicately marked with concentric lines, and slight- 

 ly punetulate toward the margins ; white or tinged with 

 brown ; the inner surface highly glossed, slightly granulated, 

 toward the margin smooth, and somewhat iridescent ; in the 

 right valve an oblique deflexed, adherent, concave tooth, and 

 a wide sinus, with a conical tooth, the margins channelled for 

 a short space ; in the left valve a sinus with a concave tooth, 

 the margins plain. Length five-twelfths of an inch, height 

 three-twelfths. 



Not uncommon in deep water off Aberdeen ; often brought 

 up on the lines adhering to actiniae, ascidia?, and other ob- 

 jects ; frequently also cast on the beach. 



In shell sand from Ugie-mouth, and Cruden Bay. 



Tellknya glabra. Brown, Illustr. PL 14. f. 19. 



4. Montacuta substrldta. Substriated Montacuta. 



Shell ovate, rounded at both ends, rather convex, with the 

 umbones nearer the broader end ; the dorsal line sloping ; the 

 valves thin, seinitransparent, faintly striated concentrically, and 

 marked with obsolete radiating stria? ; the teeth obscure in the 

 right valve ; the colour pale yellowish-grey, internally white 

 and shining. Length a twelfth of an inch, height a fifth less. 



Found by Miss Marion Macgillivray, in September, 1812, 

 in shell sand, from near the mouth of the Dee. 



Montacuta substriata. Turt. Brit. Biv. 59. PI. 1 1. f. 9, 10. 



GEXUS 5. CORBULA. 



Shell inequivalve, inequilateral, closed, or little gap- 

 ing. Right valve much longer, convex, with the umbo 

 prominent ; left valve less convex. Hinge strong, with 

 a curved pointed tooth and a cavity in the right, a spoon- 

 shaped tooth in the left valve. Internal ligament re- 

 ceived into these cavities. 



1. Corbula incsquivdlvis. Common Corbula. 

 Shell rotundato-trigonal, very inequivalve ; the right valve 



