MALACOZOA. TROPIOrODA. LAMELLIBRANCHIATA. 289 



gin ; the epidermis very delicate, greyish-yellow ; the shell 

 yellowish-white, internally glossy, with the muscular impres- 

 sions faint. Length an inch, height seven-twelfths. 



Much more delicate, more elongated, and of a more yellow, 

 or yellowish-grey tint, than young individuals of Mactra 

 solida. 



Very abundant off Aberdeen, and frequently brought up by 

 the lines. 



Mactra elliptica. Brown, Illustr. — Mactra elliptica. Forbes, 

 Malac. Mon. 48. 



4. Mactra subtrimcata. Small Triangular Mactra. 



Shell trigonal, inequilateral, rather thin, yellowish-grey or 

 greyish-white, with pale olivaceous epidermis ; the valves con- 

 vex, smoothish, with distant growth-lines ; the umbones pro- 

 minent, pointed, not central, the dorsal margin being shorter ; 

 both slopes obliquely striated ; the anterior end rounded, the 

 posterior angulate ; the inner surface glossy. Length an inch, 

 height ten-twelfths. 



Varies considerably in form and tint. 



Not uncommon along the sandy coasts ; often cast on the 

 beach, and young individuals frequently brought up by the 

 lines. 



Mactra stultorum. Penn. Brit. Zool. iv. 92. PI. 52. f. 42.— Mac- 

 tra subtruucata. Mont. Test. Brit. 93. — Mactra subtrimcata. Penn. 

 Brit. Zool. Ed. n. iv. 194. PI. 55. f. 1. — Mactra subtrimcata. Turt. 

 Brit. Biv. 70. — Mactra subtrimcata. Flem. Brit. Anira. 427. — 

 Mactra deltoides. Lamk. Svst. v. 479; Ed. n. vi. 107. 



Genus 2. Goodallia. 



Shell equivalve, inequilateral, trigonal, moderately con- 

 vex, closed at both ends. Umbones prominent. Hinge 

 strong ; one valve with a single central tooth, the other 

 with two teeth and an intermediate depressed space, for 

 the ligament ; lateral teeth elongated, with correspond- 

 ing grooves in the other valve. Muscular impressions 

 large, submarginal ; pallial impressions entire. 



1. Goodallia triangularis. Denticulate Goodallia. 



Shell trigonal, thick, opaque, smoothish, with some distant 

 growth-lines, dull white, with little gloss ; the umbones very 

 prominent, nearer the anterior end ; in one valve a prominent 



2 B 



