Fam. 2, Plate 1. 



Genus 9. TRITONIA,* Cuvier. 



Corpus oblongum, quadrilateral^ postice acuminatum, subpalliatum. Caput inferius, velo fimbriato 

 vel mucronato obtectum ; maxillis corneis. Tentacula 2 dorsalia, cylindrica, supra ramosa vel filamentosa, 

 intra vaginas retractilia. Branchial pectinatse vel plumosee, ad marginem pallialem serie unica 

 utrinque dispositse; interdum in limbum fimbriatum conjuncta?. Aperturse ani et generationis ad 

 latus dextrum. 



The genus Tritonia, well known through the Memoir of Cuvier, was one of the earliest 

 established by that distinguished naturalist from the dismemberment of the Dorides of the 

 Linnean school. It has now become the type of a family. The species contained in it do not 

 appear to be numerous, but are widely distributed through the seas of our globe. Four only 

 are natives of Britain ; the typical Tritonia Hombergii being the largest of our indigenous 

 Nudibranchs. 



Spherostoma of Macgillivray is synonymous with this genus. It was established on a 

 specimen of Tritonia Hombergii in which the buccal mass had been extruded by the animal 

 when dying; a circumstance occasionally observed in the Mollusca of this order, and giving 

 the creature a peculiar appearance, not unlikely to deceive any one unacquainted with this 

 singular habit. 



The body of Tritonia is elongated and somewhat quadrilateral, from the elevation of the 

 sides and the prominence of the ridge formed by the pallial expansion : it is broad in front and 

 acuminated behind. The head is sub-inferior and indistinct, and is covered by a fimbriated or 

 mucronated veil. The mouth is large and furnished with powerful corneous jaws, and a broad 

 denticulated tongue. There are two tentacles which are dorsal, cylindrical and solid below, but 

 divided above into numerous filaments, generally more or less pectinated or branched : they are 

 retractile within sheaths, with plain margins or nearly so. The branchiae consist of branched 

 or laminated tufts, set in single series down each side of the back, on a prominent ridge or 

 margin, formed by the rudimentary cloak, which is observable in this genus : these are some- 

 times united by intermediate filaments into a continuous expansion extending to the tail, where 

 it terminates in a point. The back is generally more or less tuberculated. The anal aperture 

 is lateral, situated on the right side of the animal ; that of the genital organs is at a short 

 distance in front of and below it on the same side. 



The individuals of this genus are carnivorous. They are very inactive and sluggish in 

 habit, though not by any means wanting in beauty, the branchial plume-like tufts redeeming 

 their otherwise heavy contour. 



* A name of Minerva. 



