450 



PSEUDOLAMELLIBRANCHIATA 



CHAP. 



open, duplicated, folded back, with pallial ocelli ; branchiae not 



concrescent with the mantle ; shell 

 with unequal " ears " at the umbo, 

 hinge- teeth lamelliform, often ob- 

 scure. Silurian . Principal 



genera: Pedum^ Clilamys^ Hiyinites^ 

 Hemij)ecten^ Amtissium, Pecten ; 

 Aviculopeeten (Palaeozoic), Oreni- 

 l)ecten. 



Fam. 5. Limidae. — Mantle edge 

 as in Pecten^ tentaculate ; shell sub- 

 equivalve, eared, fixed by a byssus 

 or free. Carboniferous . Gen- 

 era: Lima (Fig. 85, p. 179), Limea. 

 Fam. 6. Spondylidae. — Foot 

 with a peduncular appendage, no 

 byssus, numerous pallial ocelli; shell fixed by right valve, 

 surface often very spinose, two cardinal teeth in each valve. 

 Jurassic . Genera: Plicatida^ Spondylus ; Terquemia(Ij'rds'). 



Fig. 303. — Pecten pallium L., East 

 Indies. 



Fig. 304. — Spondylus 

 petroselinum Sowb., 

 Mauritius ; on a coral. 



Fam. 7. Dimyidae. — Shell ostreiform, fixed, hinge with or 

 without symmetrical teeth, two muscular impressions. Single 

 genus, Dimya (Tertiary). 



