16 GASTEROPODA. DORIDIDZ. 
The genera which compose this order have no shell; the 
respiratory organs are placed on, the sides or posterior extre- 
mity of the back, and vary in their form in each genus. The 
sexes are hermaphrodite. All the species inhabit the sea. 
Synopsis Familiarum. 
Fam. I. Dortpips. Branchie anum circumdantes, ra- 
diatee, ramosee. Anus dorsalis, posticus, medius. Pallium 
undique dilatatum. Sexuwum Organa anteriora, lateralia, dex- 
tra. Tentacula duo labialia, et duo dorsalia, annulata. Os 
rostriforme. Mandibule nulle. 
Fam. II. Eourp1ap". Branchie dorsi latera imbricantes. 
Anus et Secuum Organa lateralia, dextra; apertura communi. 
Pallium non dilatatum. Tentacula duo labialia; quatuor 
dorsalia subannulata. Os labio crasso. Mandibule nulle. 
Fam. III. Trirontaps. Branchie laterali-dorsales, ra- 
mos. Anus postico-lateralis, dexter. Pallium aliquantulum 
dilatatum. Sexuum Organa antico-lateralia, dextra. Tenta- 
cula duo dorsalia, retractilia. Os mandibulis duabus corneis 
armatum. 
FAMILY I. DORIDID~. 
Cyclobranches, Blainville. 
Branchie anum circumdantes, radiatee, ramosee. Anus dor- 
salis, posticus, medius. Pallivm undique dilatatum. Sexuum 
Organa anteriora, lateralia, dextra. Tentacula duo labialia, et 
duo dorsalia, anteriora, annulata. Os rostriforme. Mandibule 
nullee. 
Branchie radiated and branched, arranged in a circle round 
the anus, which is situated on the hinder part of the middle of 
the back. Mantle dilated on all sides. Sexual organs situated 
on the right side anteriorly. 'Tentacula two on the head, which. 
are simple; two others on the back, which are annulated. 
Mouth rostriform, without mandibles. 
