PHOLADIDA. 12% 
lateral and divergent. Base of siphons protected by corneous 
or calcareous sheaths. 
Navea, Gray, 1851. 
Distr.—3 sp. California. N. subglobosa, Gray (ev, 80, 81). 
Shell oval, widely gaping anteriorly, close posteriorly ; surface 
divided by a subcentral groove ; dorsally covered by a coriaceous 
epidermis (striated behind the interior spatulate processes), 
under which is a small transverse posterior dorsal valve. 
SupramMity JOUANNE TINE. 
Anterior ventral gap closed in the adult by a callous plate. 
PHOLADIDEA, Turton, 1819. 
Syn.—Cadmusia, Leach. 
Distr —8 sp. W. Coast of N. America, New Zealand. P. 
papyracea, Sol. (cv, 82, 83). 
Shell globose-oblong, with a transverse furrow; anterior gap 
large, closed in the adult by a callous plate; two minute acces- 
sory valves in front of the beaks. 
Animal with a fringed disk at the end of the combined siphons, 
and a horny cup at their base (in adults). 
HATASIA, Gray, 1851. Siphonal cups or valves with a tubular 
shelly prolongation. P. melanura, Sowb. 
TALONELLA, Gray, 1851. Siphonal valves without any tubular 
prolongation, and with a longitudinal and transverse fold. P. 
tridens, Gray. 
NETASTOMELLA, Carp. Based upon Ph. Darwinii, Sowb., 1865. 
The valves are posteriorly prolonged into a flattened calcareous 
eup. Differs from Jouannetia in having both valves equal, and 
from Pholadidea by the calcareous nature of the cup at the pos- 
terior end of the shell. 
JOUANNETIA, Desmoulins, 1828. 
Syn.—Triumphalia, Sowb., 1849. 
Distr.—2 sp. Philippines. 
Shell very short, subglobose, with two impressed radiating 
grooves ; right valve longest behind ; anterior opening closed by 
a callous plate developed from the left valve overlapping the 
margin of the right valve, and fixed to the single unsymmetrical 
umbonal plate. 
PHOLADOPSIS, Conrad, 1849. Valves with a single subcentral 
radiating groove. J. pectinata, Conr. (civ, 63). California. 
PARAPHOLAS, Conrad, 1848. 
Distr.—2 sp. California, Australia. Fossil; Cretaceous. P. 
Californica, Conr. (civ, 64). 
Shell oval-oblong; anterior gap closed by a thin, swollen, glo- 
