EOLIDIDJE. 



35 



subpallial margin or rudimentary mantle, in having two 

 gastro-hepatic vessels running down the back, and in the 

 dorsal position of the vent. In the last two characters it ap- 

 proaches more nearly to the Hermceidce. 



Genus FIO'NA*, Alder and Hancock. 

 [PL II. f. 2.] 



BODY elliptic-oblong : tentacles 4, subdorsal : branchial pro- 

 cesses conical, with a membranous expansion on one side, and 

 set on a subpallial margin : odontophore with a single series 

 of arched plates bearing a stout central spine and lateral 

 denticles. 



FIONA NO'BILIS, Alder and Hancock. 



Oithona nobilis, A. & H. in Ann. N. H. 2nd ser. viii. p. 291, pi. 9, 10. 

 F. nobilis, Brit. Nud. Moll. fam. 3, pi. 38 a. 



BODY stout, limaciform, of a pale buffcolour : tentacles linear, 

 smooth, broad at the base and tapering to a point above ; the 

 anterior pair placed considerably behind the margin of the 

 head: branchial processes numerous, linear-conical, rather 

 compressed, with the inner margin expanded into a membra- 

 nous frill ; the central gland is of a rich brown, the external 

 surface buffcoloured, the apices opaque bluish-white, with a 

 brilliant metallic lustre, which is observable also on the back : 

 the branchial processes or papillae are crowded without ap- 

 parent order on the sides of the back and pallial ridge, which 

 is considerably produced behind. L. 2. 



HABITAT: Two specimens of this splendid mollusk were 

 found by Mr. Cocks under a stone at Bar Point, Falmouth, 

 during a low spring- tide in 1849. It has not since been met 

 with. [Finistere (Fischer).] 



Family III. EOLI'DIDJE, D'Orbigny. 



Branchial processes linear or fusiform, set along the sides of 

 the back ; without mantle : tentacles 4 or 2, non-retractile : 

 vent lateral : gastro-hepatic system with a posterior central 

 vessel. 



* A proper name from Ossian. 



