BRACHIOPODA,. 3838 
with diverging branches; cardinal and adductor impressions 
distinct. The furrowed cones undoubtedly indicate the existence 
of spiral arms, similar to those of Atrypa (Fig. 180), but desti- 
tute of calcified supports. The upper valve sometimes exhibits 
markings derived from the surface on which the shell has grown. 
The mantle-lobes seem to have continued depositing shell 
until the internal cayity was reduced to the smallest possible 
limit. 
Fossil, 3 species. Deyonian—Trias. 
Dorsal valve Fig. 188. Ventral valve, 
CALCEOLA, Lamarck. 
Etymology, calceola, a slipper. 
Type, C. sandalina, Pl. XV., Fig. 26. Fig. 188. 
Shell thick, triangular ; valves plain, not articulated ; ventral 
yalye pyramidal; area large, flat, triangular, with an obscure 
central line; hinge-line straight, crenulated, dorsal valve flat, 
semicircular, with a narrow area (i), a small cardinal process 
(7), and two lateral groups of small apophysary (?) ridges (0) ; 
internal surface punctate-striate. 
' Fossil, Devonian, Hifel, Britain. 
The supposed Carboniferous species (Hypodema, D.K.) is, per- 
haps, related to Pileopsis. Calceola is shaped like Cyrtia, and 
its hinge-area resembles that of some Strophomenas. 
FAMILY V.—PRODUCTIDZ, 
Shell concayo-conyex, with a straight hinge-line; valves 
rarely articulated by teeth; closely appressed, furnished with 
tubular spines; ventral yalye conyex ; dorsal concave; internal 
surface dotted with conspicuous, funnel-shaped punctures; 
dorsal yalye with a prominent cardinal process; brachial pro- 
cesses (7) sub-central; vascular markings lateral, broad, and 
simple ; adductor impressions dendritic, separated by a narrow 
eentral ridge ; ventral yalye with a slightly notched hinge-line; 
