Fam. 3, Plate 38 a. 



Genus 15. FIONA,* Alder and Hancock. 



Corpus oblongum, limaciforme, subpalliatum. Caput terminals, maxillis corneis. Tentacula 4 

 subdorsalia, linearia, non-retractilia. Branchice papillosse, elongatse, membrami laterali instructae; ad 

 marginem subpallialem dorsi utrinque dispositse. Anus dorsalis, latus dextrum versus situs. Orificia 

 genitalia disjuncta, infra tentacula dextra posita. 



This genus was established by us in the eighth volume of the ' Annals of Natural History,' 

 new series, 1851, under the name of Oithona; but unfortunately, as in some other instances, 

 notwithstanding our care to avoid it, we find we had selected a name that was already 

 pre-occupied, having been used by Dr. Baird to designate a genus of Fntomostraca, in the 

 first volume of the ' Zoologist/ published in 1843. We now, therefore, substitute that of 

 Fiona. 



The genus has considerable resemblance to Bolis in its external appearance, but on a 

 close inspection, many points of difference may be observed between them. The principal 

 are the latero-dorsal anus in Fiona, and the presence of a membrane running down the side 

 of each branchial papilla ; the latter being much more firmly attached to the back than in 

 Folis. There is likewise, in Fiona, a rudimentary cloak ; the oral tentacles are placed very 

 far back, and the apertures of the- sexual organs are separated. It is with Hermaa, 

 however, that Fiona would appear to be most closely related, as is evinced not only by the 

 position of the vent, and the two genital orifices, placed far forward; but particularly by 

 the characters of the gastro-hepatic system, the vessels of which are arranged on a 

 similar plan. 



The mollusk upon which this genus is founded was discovered by Mr. Cocks, at 

 Falmouth, in 1850, and has not since been met with. It is curious that the only other known 

 species of the genus should be found at the antipodes ; the Bolide a longue queue {Eolis 

 longicauda) of Quoy and Gaimard, a New Zealand mollusk, being evidently a Fiona, as is 

 shown by the position of the anus, and the membrane of the dorsal papillae. Other points of 

 resemblance may also be traced in the tentacles and foot. 



The body of Fiona is elongated and limaciform, having the sides produced into a 

 sub-pallial expansion, which is most distinct behind. The head is terminal, bearing two 

 pairs of linear, non-retractile tentacles, both sub-dorsal. The mouth is provided with corneous 

 jaws. The branchiae are papillose and elongated, clothing irregularly the sub-pallial margin 

 along the sides of the back. A produced membranous margin or fringe runs down the 



* A proper name, from Ossian. 



