500 



MOLLUSCA 

 Tertiary and Recent. 



PHYLUM VI 



Subgenus Pavomya Gray 



young, l^oring in the softer rocks. 

 {Chaenopea INIayer). 



Panope Menard ^ {Ghjcimeris Lam. 1799, non Da Costa) (Fig. 830). Large, gaping 

 widely behind and slightly in front ; surface concentrically, or feebly sculptured ; an 

 obscure tooth in each A'^alve. Cretaceous to Recent. 



Cyrtodaria Daudin (Ghjcimeris Lam. 1801, non. Schum.). Solenoid with strong 

 epidermis. Pliocene and Recent. 



Family 44. Gastrochaenidae Gray. 



Shell substance as in Saxicava ; valves equal, widely gaping in front ; adductor scars 

 unequal, the anterior smaller ; pallial sinus deep, margins simple; area none; ligament 

 and resilium external, pjarivincular ; hinge loith a single obsolete cardinal or uliolbj 



edentulous; animal frerpbently forming 

 an external protective tube to sup)plcment 

 its burrow, but to tvhich it is in no way 

 attached. (?) Permian. Trias to Recent. 



This group stands between the Myacea 

 and Adesmacea, verging on the latter. Many 

 of its characters are adaptive, and are re- 

 peated in the Ensiplionacea, but morpho- 

 logically its relations to the Saxicavidae 

 seem close. 



Flc. 831 



Gastrochacna angusUi Desh. 

 Eocene (Sables moyens) ; 

 Valmandois, near Paiis. 



Fio. 832. 



Gastrochaena deshmg- 

 ehmnpsii Laube. Middle 

 Jura; Balin, near Cracow. 

 Internal mould of burrow 

 including one of the 

 valves, i/i. 



Gastrochaena Spengler ( Ghaena 



Retzius; Bocellaria Blainv.) (Figs. 831, 



832). Bores cylindrical or pear-shaped cavities in rock, shell, or coral. ^ Trias to Recent. 



Fistulana Brug. Secretes calcareous tubes which stand upright in the sand or 



mud. Recent. 



Superfamily 17. ADESMACEA Blainville. 



Gills with direct and reflected laminae, long, united, extended into the branchial 

 siphon ; posterior adductor usually 'in front of the visceral ganglion, anterior adductor 

 external to the cavity of the valves, exerted in a contrary sense to the posterior muscle ; 

 hinge margin reflected, edentulous; ligament obsolete; a myophoric process extending 

 ■freely into the valve from the sub-unibonal cavity. 



Family 45. Pholadidae Fischer. 



Shell cellulo-crystalline, with a thin epidermis ; valves more or less gaping in front 

 and behind,, with inconspicumis beaks and reticulate, often spinose sculpture; m the 

 A r. 



Fin. 833. 

 I'holas Uvcsqun Watelet. Eocene ; Cuise de la Mothe. 



adult supplemented by accessory shelly pieces, ahoays attached to the valves, hit rarely by 

 an exterior shelly tube like that of the Gastrochaenidae ; the antero-dorsal margins more 

 or less extensively reflected, the postero-venfral approximated; p)allial line sinuated, area 



1 Erroneously written Pnivypea by many authors. 



