266 Contribution to our knowledge of Pelagic Mollasca. [No. 4, 



Hyalaea tridentata, Gmel. pi. xxi, Fig. l. 



Anotnia tridentata, Gmelin ; Forskahlii, Chemnitz ; Chiaje. 



Cavolina natans, Abilgaard ; Cuvier. 



Caulina natans, Poli. 



Hyalaea papilionacea, Bory de St. Vincent ; Blainville. 



Hyalsea cornea, Eoissi, Larack. 



Hyalaea tridentata, Bosc ; Lamck. ; D'Orbigny ; Philippi. 



Hyalaea Chemnitziana, Peron et Lesueur. 



Hyalaea Forskahlii, Les. : D'Orbigny. 



Hyalsea tridentee, Voyage Bonite, Moll. 



Hyaloea truncata Krauss. 



Shell semi-spherical, inflated, gibbous anteriorly, lateral points some- 

 what convergent, widely cleft, lateral margin of dorsal plate wrinkled, 

 slightly reflected, inferiorly five-ribbed, terminal tooth longer than 

 the lateral ones. 



Habitat. Indian and Pacific (?) Oceans. 



Hyalaea teniobranchia, Peron, Pi. xxi, Fig. 2. 



Hyalsea Peronii, Rang. 



Shell sub-triangular, flat, semi-transparent ; lateral points wide, some- 

 what divergent ; upper third of cleft overlapped by margin of dorsal 

 plate, lower third overlapped by ventral margin ; inferiorly, three ribs 

 converge separately and narrowing unite towards the long terminal 

 tooth. 



Habitat. North Atlantic. 



Hyalsea affinis, cL'Orb., Pi. xx; Fig. 3. 



Hyalaea affinis, Desh. in Lamck. Hist. 

 (?) Hyalaea Peronii, Les. 



Shell ovoid, inflated, transparent, horny ; inferior lip very long, nar- 

 row, sinuated superiorly ; inferiorly three ribs unite in anterior half 

 of dorsal plate, and thence descend posteriorly in one more or less pro- 

 minent rib. 



Habitat. Indian and Pacific Oceans. 



