PLATE IV. 
Figs. 1, 2. Cymbulia. 
Fig. 1. Central part of the animal, seen from the right side as a transparent object; a, “shell”; b, truncated 
tin ; c, posterior appendage of the tin, cut short ; d, space between this appendage and the shell ; 
e, pallial gland ; /, entrance of the pallial cavity ; g, mouth ; h, visceral mass ; i, anus ; j, genital 
orifice, followed by the spermatic groove leading to the penis ; Jc, aperture of the penis ; l, lumen 
of the kidney ; to, aperture leading from the kidney into the pallial cavity ; n, heart ; o, central 
nervous system ; y, pallial cavity. 
Fig. 2. Stomato-gastric nervous system, seen from the left side ; a, mouth ; b, buccal mass ; c, salivary gland ; 
d, oesophagus ; e, stomach ; /, intestine ; g, buccal ganglion ; h, oesophageal nerve leading to i, the 
gastric plexus. 
Figs. 3, 4. Gleba. 
Fig. 3. a, Pallial gland ; b, outline of the shell. 
Fig. 4. Central nervous system, seen from the left side ; a, cerebral ganglion ; b, pedal ganglion ; c, left 
visceral ganglion ; d, posterior visceral or abdominal ganglion ; e, cerebral commissure ; /, otocyst ; 
g, nerves to the fin ; h, nerve to the retractor muscle of the proboscis ; i, tentacular nerve ; j, 
oesophagus ; 3, visceral (genital) nerve; left pallial nerve. 
Fig. 5. Notarchus. 
Fig. 5. Sagital section of the buccal mass, from a sketch kindly presented by Dr. Vayssiere ; a, palatine 
teeth; b, right jaw; c, radula ; d, mouth; e, oesophagus. 
Fig. 6. Dexiobranchsea, ' 
Fig. 6. Diagramatic sagittal section of the buccal mass ; a, hook-sac ; a’, hook-sac as found in Pneumonoderma; 
b, jaw; c, radula; d, mouth; e, oesophagus. 
Fig. 7. Pneumonoderma. 
Fig. 7. Transverse section of the dorsal patch; a, epithelium; b, large glandular cells; c, small central 
glandular cells. 
Fig. 8. Spongiobranchaea. 
Fig. 8. Dorsal view of the generative organs ; a, genital gland ; b, genital duct ; c, muciparous gland ; 
d, albuminiparous gland ; e, receptaculum seminis ; /, genital orifice. 
Fig. 9. Pneumonoderma. 
Fig. 9. Ventral view of the central nervous system, the cerebral commissure having been divided and the 
cerebral ganglia reflected ventrally ; a, cerebral ganglion ; b, pedal ganglion ; c, pleural ganglion ; 
d, right visceral ganglion ; e, buccal ganglion ; /, cerebro-pleural connective ; g, cerebro-pedal con- 
nective ; h, pleuro-visceral connective ; i, cerebro-buccal connective ; j, nerve from the pleural 
ganglion ; k, pedal commissure ; Z, second pedal commissure ; i., nerve to the foot ; ii., nerve to 
fin; iii., iv., lateral pedal nerves; v., vi., vii., cervical nerves; 1 , nerve from the right visceral 
ganglion; 2, 3, median nerves from the left visceral ganglion; p lateral nerve from the left visceral 
ganglion. 
Fig. 10. Clionopsis. 
Fig. 10. V entral view of the osphradium ; a, osphradium ; b, nerve ramifying in the osphradium ; c, anus ; 
d, opening of the kidney ; e, cloacal depression. 
