•ANATOMY OF TRITONIA.
G e n u s 9. TRITONIA,* C u v i e r .
Corpus oblongum, quadrilatérale, postice acuminatum, subpalliatum. Caput inferius, vélo fimbriato
vel mucronato obtectum ; maxillis comeis. Tentacula 2 dorsalia, cylindrica, suprà ramosa vel filamentosa,
intra vaginas retractilia. Branchies pectinatæ vel plumosæ, ad marginem pallialem sérié unicâ
utrinque dispositæ ; interdum in limbum fimbriatum conjunctæ. Aperturæ 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 Borides of the
Linnean school!' ’ It has now become the type of a family. The species contained in it do not
appear to be numerous, hut 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 Macgfflivray is synonymous with this genus. It was established on a
specimen of Tritonia Ktmlergii 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 pallia! 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 branchim 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 sometimes
united by intermediate filaments into a continuous expansion extending to the tail, where
it terminates in a point. The hack 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.