24 GASTEROPODA. TRITONIADZ. 
Genus 8. TRITONIA. 
Tritonia, Cuvier, Lamarck. 
Corpus posticé angustius. Branchie plurime, sessiles. 
Labia lata, membranacea. 
Body narrower behind. Branchiz many, sessile. Lips 
membranaceous and broad. 
The anatomical structure of this genus has been well inves- 
tigated by Cuvier, from whose observations it appears that the 
brain is composed of four lobes; the intermediate lobes are 
large, the lateral ones small and rounded. The anterior aspect 
of the central lobes receives two pairs of nerves from the in- 
teguments of the mouth; a third from the dorsal tentacula ; 
the fourth from the situation of the eye; the fifth and sixth 
from the muscles of the jaws; and the other pairs, to the num- 
ber of six or seven, arise from the lateral parts, and general 
muscular covering of the body, and joi the posterior and 
lateral aspects of the brain. Cuvier could not discover any 
other ganglia, nor could he satisfy himself of the completion of 
the nervous collar round the cesophagus. ; 
The jaws are horny, and, according to Cuvier, resemble 
shears. Behind them is situated a lip armed with sharp points 
turning backwards, whose office is to convey the broken food 
into the cesophagus, which is membranaceous and longitudi- 
nally folded within. The stomach is membranaceous, slightly 
dilated, and imbedded in the liver. The duodenum is short, 
striated longitudinally within, which, after making one bend, 
terminates in the anus, situated behind the middle of the right 
side. 
1. Trrronta HomBereit. Plate VII. fig. 2. 
T. dorso tuberculato; tuberculis ineequalibus irregulariter 
rotundatis, lateribus leevibus. 
Tritonia Hombergii, Cuv. Ann. du Mus. i. 483. pl. 31. fig.1, 2; 
Mém. sur les Moll. fig. 1, 2; Lam. H. N. des Anim. sans 
Vert. vi. 304. 
Long. corp. 1-23 poll. 
Habitat in Danmoniz mari, rarissima. 
