388 



manual of the molltjsca. 

 Family YII. — Discinid^. 



Shell attached by a jDedicle, passing tlirougli a foramen in tlis 

 ventral valve ; valves not articulated ; minutely punctate. 



Fig. 195. Crania.* 



Fig. 196. DiscinaA 



Animal with a highly vascula-r mantle, fringed with long 

 horny setse ; oral arms curved backwards, returning upon them- 

 selves, and ending in small spires directed downwards, towards 

 the ventral valve. 



DisciNA, Lamarck. 



Orbiculoidea 



Synonyms, Orbicula, Sby. (not CuvierJ). 

 (elliptica), D'Orbigny. Schizotreta, Kutorga. 



Types, D. lamellosa, PI. XY., Fig. 31. (=D. ostreoides, 

 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. 



^?2iV/2aZ 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, -vrith 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 ai-e displaced forwards, in order to show their spiral terminations '. 

 V is the expanded surface of the pedicle ; the mouth is concealed by the overhanging 

 cirri. The mantle-fringe is not represented. 



X The Orbicula of Cuvier was the Patella anomala, Miili (= Crania), as pointed out 

 by Dr. Fleming, in the " History of British Animals," 1828. 



