ACEPHAliA TESTACEA. 105 



near the lunulo, is a little plate en chevron. The tubes are united 

 and short *. 



Some of them are found on the coast of France, 



In the Lavignons, the lateral plates are almost effaced, but a single 

 small tooth is observable near the internal ligament ; there is also a 

 second and internal ligament. The posterior side of the shell is 

 the shortest ; the valves are somewhat open, and the tubes are sepa- 

 rate and very long, as in the Tellinye. 



There is one found on our coast, Mya hispanica, Chemn. VI, 

 iii, 21, which lives in the ooze at the depth of several inclies f. 



FAMILY V. 



INCLUSA |. 



The mantle open at the anterior extremity, or near the middle 

 only, for the passage of the foot, and extended from the other end 

 into a double tube, which projects from the shell, whose extremities 

 are always gaping. Nearly all of them live buried in sand, stones, 

 ooze, or wood. Those of the genus 



Mya, Lin. 



Have but two valves to their oblong shell, the hinge of which varies. 

 The double tube forms a fleshy cylinder, and the foot is compressed. 

 The different forms of the hinge have furnished Messrs. Daudin, La- 

 marck, &c., with the following subdivisions §, in the first three of 

 wliich the ligament is internal. 



Lutrabia, Lam., 



The Lutrarite, like the Mactree, have a ligament inserted into a 

 large triangular cavity of each valve, and before that cavity a small 



* After abstracting the Lavignones and Luirariee, the genus Mactra of Gmelin 

 miy remain as it is ; the species, however, are far from being well distinguished. 

 Add, Mija uusfralis, Chemn., VI, iii. 19, 20. 



The Erycin^, Lam., are neighbours of the Mactra, and are but badly charac- 

 terized. See Ann. du Mus., IX, xxxi, and Deshayes, Coq, Foss., I, vi ; part of 

 them, perhaps, belong to the Crassatellse. The Anphidesm^. Lam., or Ligul^, 

 INIontag., appear to approach the Mactrae, but they are too imperfectly known to 

 have any distinctive character assigned to them. 



■f- Improperly called by Gmelin Mactra piperata. 



Add, Mactra papyracca, Chemn., VI, xxiii, 231 ; — Muct. complanata. Id., xxiv, 238 ; 

 — Mya nicobarica, Id., iii, 17, 18. 



X M. de Blainville makes two families of this one, his Pyloridila and Adesma- 

 CEA. The last includes Pholas, Teredo, and Fistidana : the first, all the others, and 

 even Aspergillum. There are numerous genera established in this family too slightly 

 characterized to permit us to adopt them. 



§ N.B. Half the Myffi of Gmelin neither belong to this genus, nor even to this 

 family, but to Vulsella, Unio, Mactra, &c. 



