MOLLUSCA. 
427 
four wings, formed in pairs; head slightly projecting; two ten¬ 
tacula, dilated above, and compressed towards their base; 
branchiae disposed in tufts over the internal surface of the 
wings ; anal orifice, and the opening for generation, situated on 
the right side* 
Genus 31. — TRITONIA.— Cuvier. 
Generic Character. —Body creeping, ovate-oblong; back con¬ 
vex ; head short, broad, and sessile, with two retractile tenta- 
cula, either simple or divided; branchiae dorsal, in branched tufts, 
placed in a double row; anus and orifice for generation on the 
right side. 
Genus 32. —EOLIS.— Lamarck. 
Generic Character. —Body oblong, creeping, attenuated, acute 
behind, and somewhat convex above; destitute of a man¬ 
tle ; head short, with four or six tentacula; branchiae projecting, 
disposed along the back in rows, shaped like scaly plates, papil¬ 
lose, or like cirri; anal and orifice of generation situated in the 
right side. 
Genus 33.—GLAUCUS.— Cuvier. 
Generic Character. —Body elongated, subcylindrical, and ge¬ 
latinous, terminating posteriorly in a slender subulate tail; head 
short; four conical tentacula disposed in pairs ; three or four 
pairs of lateral, opposite, and pal mated branchite, digitated at 
their summit, the posterior ones nearly sessile; anal and gene¬ 
rative orifices placed laterally. 
ORDER V.—PTEROPODA. 
Animals destitute of any foot for locomotion, and of arms for 
seizing their prey; provided with two opposite and similar fins 
fitting them for swimming; body free and floating. 
Genus l.-PNEUMODERMON_ Cuvier. 
Generic Character .—Body free, naked, soft, and oval; head 
distinct; mouth terminal, with two lips; at the side of the 
