16D WORMS. TESTACEA. 43. 44. 



triangular shape than V. vcrrucosa and not slightly truncate on tie 

 anterior part, whitish,, with 15 or 16 obtuie very regular but not 

 membranaceous wrinkles. 



279. V* triangidaris. Somewhat triangular, equally slop- 

 ing each side under the beak, yellowish-white, with a 

 few antiquated ridges : in one valve 2 teeth, and a 

 lateral semilunar lamina ; in the other 3, 2 of them 

 diverging. 



Montague Bri. Shell, app. p. 577. tab. 17. f, i. 



Shell half an inch long, nearly as broad j smooth within : beak 

 cental, very prominent, a little oblique, with a lanceolate de- 

 prefsion under it : one valve with 2 strong teeth, one cloven, tho 

 other triangular with a semilunar lamina near it; the other valve 

 with 3 teeth. 



^80. V. spinifera. Suboval, subtriangular, with fine equi- 

 distant raised ridges becoming confluent in pairs at 

 the anterior side and forming obtuse reflected spines. 



Montague Brit. Shells, app. p. 577. 



Shell half an inch long;, rather more broad, yellowish-white, with 

 numerous parallel somewhat reflected ridges ending on the margin 

 of the cartilage slope in short spines, within white smooth : beak 

 nearly central, a little turned, with a lanceolate deprefsion beneath 

 it : hinge with a single tooth and a small cavity and a remote late- 

 ral lamina in one valve ; in the other valve 2 teeth. 



43. CHAM A. 



581. Ch. Cor. Subglobular, heart-shaped, slightly stri- 

 ate, gaping at the anterior slope: beak much 

 incurved. 



Donovan tab. 134. Lister conch, t. 275. f. in. 



Shell near 3 inches wide, strong, thick, covered with a yellow- 

 brown skin under which it is varied with brown and white, slightly 

 wrinkled transversely, with the margin entire : beak reddish, 

 large, prominent, twisted inwatda : hinge strong, with ttattish 

 teeth. 



44. ARCA. 4rk-$hell. 



282. A. pttosa. Suborbicular, exactly equilateral, faintly 

 striate longitudinally with transverse wrinkles, co- 

 vered with a villous skin under which it is marked 

 with zigzag brown lines. 



Br. Zoo!, t. 58. /. 58. Donou. t. 37. A. Glycymcris. 



Shells inches and a half wide, covered with a dark-brown hairy 

 skin, beneath which are chesnut or orange angular stripes ; within 

 white with a crenate margin ; beak prominent, central, straight. 



283. A. Glycymeris. Suborbicular, a little irregular, 

 faintly striate, covered with a villous skin, under 

 which it is marked with yellowish spots or bands. 



Linn. Trans, viii./>. 95. tab. 3>f. 3. 



Shell resembling the last, bu.. is more gibbous, and not quite 

 equilateral, withia white with a crenulate margin: teeth about 10, 

 transverse. 



284. A. lactea. Rhombic, yellowish- white, covered with 

 a brown hairy skin, closely and regularly striate 

 longitudinally with a few concentric ridges. 



Donovan t. 135. Br. Zool. t. 58. /. 59. 



Shell an inch and a half long, 3 quarters of an inch broad, some- 

 times reticulate, sometimes rounded at both ends, sometimes a 



