130 MONOMYARIA. 



Section III. — Ligament marginal and elongated. 



TRIBE I. MALLEACEA. 



With foliaceous shells, more or less inequivalve ; having 

 the ligament marginal, somewhat linear, and either simple 

 or interrupted by crenulations. 



Genus 22.— MELEAGRINi\ Lamarck. 



Generic Character. — Somewhat equivalve, rounded and 

 scaly on the outside : a sinus at the posterior base of the 

 shell for the passage of the byssus, at which place the left 

 valve is notched and narrow; hinge linear, and destitute of 

 teeth ; ligament marginal, elongated, and placed nearly ex- 

 terior, and dilated in the centre. 



In many respects resembling Avicula, but differing in being equi- 

 valve, and always without the elongated transverse base, on the car- 

 dinal tooth. The sloping sides of the opening, admitting the passage 

 of the byssus, are perceptible on both valves, which is never the case 

 with Avicula, where a notch answers the same purpose. 



Meleagrina mar gar it if era. — The Pearl-bearing Me- 

 LEAGRiNA. Plate XV. fig. 10. Somewhat square, com- 

 pressed; undulated, and transversely striated, with a series 

 of lamelliform longitudinal scales; greenish on the outside 

 and perlaceous within. Ten or twelve inches long. In- 

 habits the Indian seas. 



Genus 23 AVICULA.— Lamarck. 



Generic Character Shell inequivalve, fragile, with the 



base straight, transverse, and produced at both extremities, 

 the anterior of which is caudiform ; valves oblique ; the left 

 one emarginate, with a sinus or notch, through which the 

 byssus passes; hinge linear, with one tooth in each valve, 

 under the beaks ; ligament linear and marginal, placed in a 

 long narrow groove. 



Avicula Anglica. — The English Avicula. Plate XV. 

 fig. 11. Wing moderate, obliquely curved; yellowish fawn- 



