The Cambridge natural history . th adductorswell developed, heart with two aortae, branchiae free, withoutinterlamellar junctions, no siphons; renal and generative aper-tures distinct. Fam. 1. —Mantle edge with composite eyes; shellround or trapezoidal, solid, often with stout bushy periostracum;ligament often external, on a special area; hinge with numer-ous lamelliform teeth. Ordovician . Principal genera : Area (inch Barhatia,Scaph%da, and Gucullaeci), heart dorsal torectum; Pectuncidus, Glomus^ Lvmo])sis;Trinacria and Nucidina (Tertiary). Fam. 2. Trigoniidae.—Foot large,hatchet -
The Cambridge natural history . th adductorswell developed, heart with two aortae, branchiae free, withoutinterlamellar junctions, no siphons; renal and generative aper-tures distinct. Fam. 1. —Mantle edge with composite eyes; shellround or trapezoidal, solid, often with stout bushy periostracum;ligament often external, on a special area; hinge with numer-ous lamelliform teeth. Ordovician . Principal genera : Area (inch Barhatia,Scaph%da, and Gucullaeci), heart dorsal torectum; Pectuncidus, Glomus^ Lvmo])sis;Trinacria and Nucidina (Tertiary). Fam. 2. Trigoniidae.—Foot large,hatchet - shaped, with ventral disc; nobyssus, mantle edge with ocelli ; shellsub-trigonal, hinge-teeth few, strong; in- ^ o^i m ? ? ,? terior violet - nacreous. Devonian . Fig. 301. — Tngonia joecti- nata Lam., Sydney, Genera: Trigonia; Mi/ojjhoria and Schiz- ? odus (Trias), Cyrtonotus (Devonian). Sub-order III. Mytilacea.—Mantle edges fused at one point,anal orifice distinct, anterior terminal adductor small, one XVI PSEUDOLAMELLIBRANCHIATA 449 branchiae with interfoliaiy junctions, genital glands penetratingthe side of the mantle and opening by the side of the ^i. Mytilidae.—Byssus well developed, shell more or less equivalve, oval, broad ; hinge-teeth evanescent. Devonian . Principal genera: MytilusJ Myalina, Septifer, Modiola, Lithodomus,Crenella, Dacrydliun, Myrina, Idas, Modiolaria, Modiolarca. Order III. Pseudolamellibranchiata Mantle edges entirely open, foot little developed, anterioradductor usually aborted, branchial filaments reflected, with inter-lamellar junctions, which are sometimes vascular; genital glandsopening into the kidneys or close to the apertures of the kidneys. Fam. 1. Avicididac.—Foot long, tongue-shaped, byssogenousapparatus well developed, branchiae concrescent with the mantle,adductor muscle sub-central, at times a small anterior adductor,siphons absent; shell usuallyinequivalve, dorsal margin r~rstraight, often very long, ~^^
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
