MALACOZOA. TROPIOPODA. LAMELLIBRANCHIATA. 291 



impressions large, distant, the anterior elongated, the 

 posterior roundish. 



The Lutrarise, so named on account of their living in 

 mud, lutum, differ little from the Mactrse. 



1 . Lutrdria elliptica. Elliptical Lutraria. 



Shell elliptical, compressed, thin, concentrically striated, with 

 a yellowish or dusky grey epidermis ; the surface of the valves 

 brownish-white ; both ends rounded and gaping, the anterior 

 much shorter ; the plicate tooth of the left valve prominent ; 

 the inside white, smooth, with a very large sinus in the pallial 

 impression. Length five inches, height three. 



Young shells are extremely delicate, hyaline-white, and 

 transparent. 



Not very uncommon along the sandy shores; also in the 

 Estuary of the Ythan. 



Mactra lutraria. Linn. Syst. Nat. i. 1126. Concha longalataque, 

 &c. Lister, Anim. Angl. 170. PI. 4. f. 19. Mactra lutraria. Penn. 

 Brit. Zool. iv. 92. PI. 52. f. 44. Lutraria elliptica. Lamk. Syst. v. 

 468; Ed. n. vi. 90. Lutraria elliptica. Turt. Brit. Biv. 65. Mac- 

 tra lutraria. Penn. Brit. Zool. Ed.n. iv. 195. PL 55. f. 3. Lutraria 

 vulgaris. Flem. Brit. Anim. 464. Mactra lutraria. Mont. Test. 

 Brit. 100. 



2. Lutrdria Listen. Lister's Lutraria. 



Shell roundish-triangular, compressed, thin, smoothish, the 

 concentric striae being prominent only toward the posterior 

 margin, which is longer, but the lines of growth conspicuous, 

 and the surface farther marked with faint divergent striae; 

 umbones small, rather pointed ; the colour dull white, tinged 

 with grey or reddish. Length two inches, height an inch and 

 three-fourths. 



In the muddy Estuary of the Ythan, opposite and above 

 Newburgh, where it was gathered by Mr. Leslie and myself 

 in April, 1 842 ; and in the Estuary of the Dee, where it was 

 found by Miss Isabella Macgillivray, along with Tellina soli- 

 dula, and Amphidesma album, in September. 



According to Montagu, " the animal has two slender tubes 

 of a yellowish colour, placed near together at the anterior end ; 

 one, about three inches long, is thrown about in search of food, 

 such as insects ; which may be seen passing up this transparent 

 syphon, with the current of water it is continually taking in, 

 and discharging at the shorter tube, placed nearer to the hinge, 

 retaining only the nutritious matter; but it occasionally ejects 



