BRAOHIOPODA. 787 
Euractinella, Bittner. 1890. 
Shells with short corresponding ribs, obscure cardinal area 
and double spirals. 
f| 
Frias. 334, 835. Huractinella contraplecta, Miiuster (sp.). (BiTTNER.) 
Type, Huractinella contraplecta, Minster (sp.). 
Distribution. Triassic. 
Anisactinella, Bittner. 1890. 
Shells with the ribs on the valves alternating in position; car- 
dinal area, deltarium and cardinal process well developed. 
Spiral cones duplex, the intercalary cones giving off a process in 
ea 
ae 3 
be 
Fies. 836-838. Anisactinella quadriplecta, Miinster (sp.). (BITTNER.) 
umbonal region which returns to join the jugum, as in Mrrisra 
and MerisrEe.a. 
Type, Anisactinella quadriplecta, Miinster (sp.). 
Distribution. Triassic. 
Retzia, King. 1850. 
(Plate 36, figs. 3-7.) 
Shell elongate-oval, rather broad over the pallial region. 
Surface covered with rather coarse, angular, usually simple 
plications. There is a trace of an indistinct median sinus on the 
pedicle-valve in which the plications are slightly smaller than 
those adjoining. The umbo of the pedicle-valve is incurved and 
its apex truncated by a circular foramen. The deltidial covering 
is triangular, flat or arched by the incurvature of the beak; the 
deltidial plates are firmly anchylosed into a single piece and the 
original line of symphysis is represented by a thickened ridge. 
The edges of the cardinal area are well defined, but not alate on 
either valve, the beak and area of the brachial valve being 
39 
