66 



** With a single accessory valve. 



Dorsal valve lanceolate ; umbonal processes reflexed, 

 closely applied. Shell oblong-ovate Genus Barnea, Leach. 



Dorsal valve ovate-cuneiform; umbonal processes re- 

 flexed, cellular beneath. Shell oblong-ovate Genus Monothyra, Tryon. 



Dorsal valve small, transverse, posterior, under a cori- 

 aceous epidermis. Hinge plates produced and reflexed. 

 Shell ovate Genus Navea, Gray. 



*** Destitute of accessory valves. 

 Beaks protected by a membrane. Valves ovate. ..Genus Zirph^ea, Leach. 



Subfamily JOUANNETIN.E. 

 Anterior ventral gap closed in the adult by a callous plate. 

 * With three dorsal accessory valves. 

 Anterior dorsal plates two, placed side by side, 

 posterior to which is a central plate, directly over the 

 umbones. Base of the siphons protected by reflected 

 appendages Genus Penjtella, Valenciennes. 



** With two dorsal accessory valves. 



Dorsal valves small. The base of the siphons pro- 

 tected in the adult by a subtestaceous cup-shaped 

 appendage, which is absent in young individuals. 

 Valves ovate Genus Pholadidea, Turton. 



Surface impressed by two oblique sulci, extending 

 from the beaks to the margins. Shell ovate-oblong. 

 Valves equal Genus Parapholas, Conrad. 



*** With a single accessory valve. 



Shell globose, hinge plates not reflexed ; inequivalve, 

 the left valve overlapping the right Genus Jouannetia, Desmoulins. 



Shell ovate-oblong, accessory valve lanceolate or 

 peltate. Equivalve; the surface impressed by one or 

 more furrows Genus Martesia, Leach. 



Index to the species o/PholadidjE. 

 Anchomasa Pennantiana, Leach = Bar- Dactylina candeana, D'Orb 



nea parva, Penn. 

 Barnea Australasia 3 , Gray. 



" Bakeri, Desh.= B. Burmanica'? 



" Burmanica, Philippi. 



" Candida, Linn. 



" Erythraea, Gray. 



" fragilis, Sowb. = Manillensis, 



Philippi. 

 " lanceolata, D'Orb. 

 " Manillensis, Philippi. 

 " parva, Pennant. 

 " similis, Gray. 

 " subtruncata, Sowb. 

 Cadmusia Solanderiana, Leach = Phola- 

 didea papyracea, Soland. 

 Dactylina Campecbensis, Gruel. 



" Gray,=D. Chi- 



loensis (part.) 



D. Cam- 

 pechensis. 

 " Chiloensis, King. 

 " dactylus, Linn. 

 " orientalis, Gniel.= Monothyra 

 orientalis, Gm. 

 Jouannetia Cumingii, Sowb. 



" Darwinii, Sowb.= Penitella 



penita. 

 " globosa, Quoy: 



" globulosa, Quoy=J. globosa. 



" pectinata, Conrad. 



u pulcherrima, Sowb.= J. pec- 



tinata. 

 Martesia acuminata, Sowb. = M. calva. 

 " aperta, Sowb. 

 V Australis, Gray. 

 " branchiata, Gould. 

 " Cali/ornica, Conr. = Parapho- 

 las Californica. 



