HALACOZOA. TROPIOPODA. LAMELLIBANCHIAYA. 297 



slightly glossy, very minutely pimctulate, at the posterior end 

 roughish, especially in the triangular space formed by a ridge 

 from the umbo to the lower angle of the truncation ; the car- 

 dinal lamina or tooth rather thick, running obliquely forward, 

 and rounded at the anterior end, beyond which is a deep sinus ; 

 the colour white, the inside glossy. Length about an inch and 

 a-half, height an inch. 



A perfect individual found by me in the Spring of 1 842 ad- 

 hering to a fishing-line at Footdee. 



Mva piibescens. Mont. Test. Brit. 40. — Tellina fragilis. Penn. 

 Brit.'Zool, iv. 86. PI. 47. f. 26. — Auatina pubescens. Turt. Brit. 

 Biv. 45. PI. 4. f. 3. — Ampbidesma piibesoens. Flem. Brit. Anim. 

 431. — Thracia pubescens. Lamk, Syst Ed. u. vi. 83. 



Family XI. — Myina. 



Animal oblong or elliptical, compressed ; with the 

 mantle closed beneath, open in front for the passage of 

 the foot, and forming behind two long tubes, united or 

 separated ; a small, compressed, tapering foot. 



Shell oval, elliptical, or oblong, generally inequivalve, 

 inequilateral, gaping at both ends, frequently covered 

 with an epidermis ; the hinge with a concave projecting 

 process or tooth in one valve, and a corresponding de- 

 pression in the other, for the internal ligament ; the 

 muscular impressions distant, large. 



The Myinse have no external ligament, but yet differ 

 little essentially from the Mactrinse, the hinge being 

 formed on the same plan in both families. 



Genus 1. Mya. Gaper. 



Animal ovate or oblong, a little compressed. The 

 lobes of the mantle very delicate, but thick at the bor- 

 ders, which cohere, and forming behind a broad com- 

 pressed muscular double tube enveloped by a membran- 

 ous layer, and having its orifices radiated. Foot very 

 small, much compressed, tapering, emerging by a small 

 slit in the mantle. Branchise moderate, unequal, striate. 

 Mouth small, with two pairs of striated appendages. 



Shell ovate or oblong, inequivalve, inequilateral, con- 

 vex, gaping at both ends, concentrically striated, covered 



