ACEPIIALA TESTACKA. 419 



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

 rate and very long, as in the Tellings. 



There is one found on our coast, 31ya hispanica, Chemn. VI, 

 iii, 21, which lives in the ooze at the depth of several inches'!). 



FAMILY V. 



INCLUSA(2). 



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(3), in the first three of 

 which the ligament is internal. 



LuTRARiA, Lam., 



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

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

 tooth en chevron; but the lateral plates are wanting; the gap of the 

 valves is very wide, particularly at the posterior extremity, through 

 which passes the thick, double, fleshy, respiratory and anal tube, a 

 disposition which attaches them to this family. The foot, which 

 issues at the opposite end, is small and compressed. 



(1) Improperly called by Gmelin Madra piperata. 



Add Madra papyracea, Chemn., VI, xxiii, 231; Mad. complanata, Id., xxiv, 

 238; Ml/a nicobarica, Id., iii, 17, 18. 



(2) M- de Blainville makes two families of this one, his PnoRiDEA and Adesma- 

 CEA. The last includes Pholas, Teredo, and Fistulana,- 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- 



(3) N.B. Half the Myae of Gmelin neither belong to this genus, nor even to this 

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



