CLASS IV. ACEPHALA. liii 



ORDER IX. — Cyclobranchiata. , 



The gills, in the forms of leaflets, are situated under the edge of 

 the mantle. In other respects the order is assimilated to the last. 



Genus. ^ Excmiple of Species. 



I. Patella, L Patella, Gm. 



IL' Chiton, L Chiton, L. 



CLASS IV.— ACEPHALA. 



In this class there is no apparent head, the principal ganglion of 

 the brain being over the mouth, which is situated at the bottom, or 

 between the folds of the mantle. 



ORDER I. — AcEPHALA Testacea. 



In this order, the animals have four branchial leaflets. All the 

 bivalves, and many multivalves, belong to it. 



Family. Genus. Subgenus. Example of Species. 



^ f\. Radiolites, Lam. 



I.Acarda,5ra^. l2. %^hexM\\tes,Lamethe- 



Ostracita, Za<o f/l'^ , • 

 ■^ ' \ o. Calceolaria 



1 eyrouse . . i 4. Hippurites 



V5. Batollthes, ilfow//. 



f 1. Ostrea, prop. Brug.. Os. edulis, L. 



\ 2. Gryphaea, Zaw Gr. tricarinata 



II. Ostrea, Zm. kS. Pecten, Brug Os. maxima, L. 



J 4. Lima, Brug Os. lima, L. 



V.5. Pedum, Brug Os. spondyloidea, Gm, 



III. Hinnita, Defr Hinnita gigantea, Gray 



IV. Plagiostoma, Sowerhy Pi. gigas. Sow. 



^V. Pachytes, Dcfr Pac spinosus, De F. 



