ACKl'HALA TE8TACEA. 105 



the lunulf, is a little plate en chevron. The tubes an- united 

 and short *. 



Some of them are found on the coast of France. 



In the LA VIGNONS, 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 Tellinae. 



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

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



FAMILY V. 



INCLUSA J. 



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. 

 'I' In* 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 

 which the ligament is internal. 



LUTRARIA, Lam., 



The Lutrariue, like the Mactrae, have a ligament inserted into a 

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



* After abstracting the Lariynones and Lutraria, the genus MACTRA of Gmelin 

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

 Add, 3fyrt austrulis, Chemn., VI, iii. 19, 20. 



The ERYCIN.E, 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 Crassatellee. The ANPHIDESMJR. Lam., or LIGUL^E, 

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

 have any distinctive character assigned to them. 



t Improperly called by Gmelin Mactra piperata. 



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

 Afya Hicobarica, Id., iii, 17, 18. 



t M. do Hlainville makes two families of this one, his PVLORIDEA and ADESMA- 

 CEA. The last includes Pholtts, Teredo, and Fistulana; the first, all the others, and 

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

 characterized to permit us to adopt them. 



$ N.B. Half the Myac of Gmelin neither belong to this genus, nor even to this 

 family, hut to Vulsella, Unio, Mactra, *cc. 



