26o 



THE LAMELL1BRANCHIA 



Odontoperna, Freeh ; fossil from the Trias. 

 from the Jurassic to the Cretaceous. 



Inoceramus, Sowerby ; fossil 



SUB-ORDER 4. PECTINACEA. 



Lamellibranchia with an open mantle and devoid of an anterior 

 adductor muscle. The gills are folded, and the filaments at the summits 

 and bottoms of the folds are different from the others. The gonads are 

 contained in the visceral mass and generally open into the kidneys. 

 Foot usually rudimentary. 



I 



Pecten jacobaeus, ventral aspect, a, anus ; e, pallial eyes ; /, foot ; g, gill ; h.a, posterior 

 adductor; i, intestine; /, lips; l.p, labial palps; m, mouth; or, ovary; pa, mantle (reflected 

 edge) ; p.c, pallial cavity ; sh, shell ; t, testis. (After Poli.) 



FAMILY 1. VULSELLIDAE, Adams. Mantle open ; foot without byssus ; 

 the shell high and the hinge without teeth. Genus Vulsella, Lamarck. 

 FAMILY 2. AVICULIDAE, Swainson. Foot provided with . a very stout 

 byssus (Fig. 236). The gills fused to the mantle ; shell very inequilateral ; 

 the cardinal border straight, provided with two auriculae, of which the 

 posterior is the longer. Genera Avicula, Bruguiere ; the auriculae of 

 the shell very prominent ; heart attached to the ventral face of the 

 rectum ; British ; fossil from the Devonian to the present day. 

 Meleagrina, Lamarck ; shell sub-quadrangular, the auriculae not very 

 prominent. A species of this genus, Meleagrina margaritifera, from 

 the Indian Ocean, Persian Gulf, etc., forms precious pearls. Malleus, 

 Lamarck ; shell irregular, high and narrow, with broad subequal 

 auriculae. The following genera are exclusively fossil : Limopteria, 



