388 MANUAL OF THE MOLLUSCA, 
FAMILY VII.—DIscInIpDz. 
Shell attached by a pedicle, passing through a foramen in the 
yentral valve; valves not articulated ; minutely punctate. 
Fig. 195. Crania.* Fig. 196. Discina.} 
Animal with a highly vascular mantle, fringed with long 
horny sete; oral arms curved backwards, returning upon them- 
selves, and ending in small spires directed downwards, towards 
the ventral valve. 
Disctna, Lamarck. 
Synonyms, Orbicula, Sby. (not Cuyierf). Orbiculoidea 
(elliptica), D’Orbigny. Schizotreta, Kutorga. 
Types, D. lamellosa, Pl. XV., Fig. 31. (=D. ostresides, 
Lamarck.) 
Shell orbicular, horny ; upper valve limpet-like, smooth or 
concentrically lamellose, apex behind the centre; lower valve 
flat or conical, with a sunk and perforated disk on the posterior 
side; interior polished; lower valve with a central prominence 
in front of the foramen. 
Animal transparent; mantle lobes distinct all round; labial 
folds united, not extensile, ; alimentary canal simple, bent upon 
itself ventrally, and terminating between the mantle-lobes on 
the right side. There are four distinct adductor muscles as in 
* Dorsal valve, with the animal, seen by removing the mantle, 
+ The animal as seen on the removal of part of the lower mantle-lobe ; the extremities 
of the labial arms are displaced forwards, in order to show their spiral terminations : 
p is the expanded surface of the pedicle; the mouth is concealed by the overhanging 
cirri. The mantle-fringe is not represented. 
t The Orbicula of Cuvier was the Patella anomala, Miill (= Crania), as pointed out 
by Dr. Fleming, in the “‘ History of British Animals,” 1828, 
