The Cambridge natural history . angular, anterior margin short or trun-cated, with a deep lunule. Single genus,Lunulicardium (Palaeozoic). Fam. 3. Tridacnidae.—Mantle ori-fices widely separated, foot short, bys-siferous, no anterior adductor; shellequivalve, large, thick, usually gapingin front, one cardinal tooth and one oreach valve, no pallial sinus. Miocene—Hippopus. The muscular power of the great Tridoxna is caught between their gaping valves, a mans hand or footcan scarcely be withdrawn. Two valves of 2\ gigns in the BritishMuseum weigh respectively 154 and 156 lbs. FA:\r.
The Cambridge natural history . angular, anterior margin short or trun-cated, with a deep lunule. Single genus,Lunulicardium (Palaeozoic). Fam. 3. Tridacnidae.—Mantle ori-fices widely separated, foot short, bys-siferous, no anterior adductor; shellequivalve, large, thick, usually gapingin front, one cardinal tooth and one oreach valve, no pallial sinus. Miocene—Hippopus. The muscular power of the great Tridoxna is caught between their gaping valves, a mans hand or footcan scarcely be withdrawn. Two valves of 2\ gigns in the BritishMuseum weigh respectively 154 and 156 lbs. FA:\r. 4. Chamidae.—Mantle orifices widely separated, footshort, no byssus, Ijoth adductors present, ovary invading the mantle lobes; shell fixed, irregu-larly inequivalve, uml:)ones spiral,ligament external, cardinal teethoften a mere ridge, anterior lateral-strong, nearly central, no pallialsinus. Jurassic . Genera : Fig. 308. — Cardium (Hemicar-dium) cardissa L., East ludies. two posterior laterals in—. Genera : Tridacna,. Chama; Diceras (Jurassic), attachedby one umbo, umbones very promi-nent, teeth strong; Hcterodiccras(Jurassic), Rcquienia (Cretaceous), A - B Fig. 309.—A,Requienia ammoneaGoldf., Neocomian, x ^; B, iiipimrites hft valve widely Spiral, attached coniu-vaccimim Goldf., Cretaceous, i , i •, • i , i , „, ,11 xi. «, right valve;/.point of fix- ^O tlie umbo, right valve small, ture. (From Zittel.) teeth culum, teeth obsolete;Secondary strata). fitting on the other as an oper-Toucasia, Apricardia, 3Iatheronia (all 456 EULAMELLIBRANCHIATA—MYACEA chap. The four succeeding families require special study in a workon Palaeontology. Fam. 5. Monopleuridae.—Shell very inequivalve, left valveoperculiform, right conical or spiral, fixed at the apex, ligament prolonged in external grooves. Cretaceous —. Genera : Monopleura, Valletia. Fam. 6. Caprinidae.—-Shell very inequivalve, thick, free orfixed by apex of right valve, which is spiral or conical, left v
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
