TRITONIA. 



hepatic branch of the same; j,j,j,j, afferent branchial veins from the liver- mass; #, retracted 

 penis ; I, testis ; m, dilated portion of the oviduct ; n, constricted portion of the same ; o, o, 

 mucus-gland in connexion with the female parts ; p, female channel ; q, spermatheca ; r, 

 vagina, leading from the external orifice to the same; s, oesophageal ganglia, distributing 

 nerves to the various organs ; t, t, the eyes. 

 Fig. 3. Side view of the buccal mass: — a, channel of the mouth; b, oesophagus; c, salivary glands; 

 d, outer edge of jaw ; e, e' , two sets of muscles for closing the jaws ; /, muscles to aid in opening 

 the same ; g, lingual muscles. 



4. Side view of the buccal mass, with one jaw and part of the muscles removed to exhibit the 



tongue : — a, oesophagus; b, cutting edge of jaw; c, hinge cut through ; d, d' , two sets of muscles 

 for closing the jaws, cut through; e, muscles to aid in opening the same; /, anterior or 

 expanded portion of the dentigerous membrane ; g, end of the posterior or tubular portion of 

 the same ; h, portion of the inner layer of lingual muscles for drawing the sides of the tongue 

 together ; i, i, principal stratum of the outer layer of muscles for drawing the tongue upwards 

 and backwards, the two outer strata being almost entirely removed; j, a portion of one of 

 the outer strata of the same, for rotating the tongue forward, the outer or external one being 

 removed. 



5. Dentigerous membrane removed from its muscular support : — a, anterior or expanded portion 



of the membrane ; b, posterior or tubular portion of the same. 



6. A portion of one of the row3 of lingual spines : — a, a, lateral spines ; b, central plate ; c, c, the 



two lateral plates. 



7. Inside view of jaws : — a, hinge ; b, cutting edges. 



8. Outside view of a single jaw : — a, point of articulation ; b, cutting edge. 



9. Cerebral ganglia : — a, a, cerebroid ganglia ; b, b, branchial ; c, c, pedial ; d, olfactory ; e, optic ; 



/, buccal; g, g, gastroesophageal ; h, great sub- oesophageal collar; i, i, buccal collar; 1, 

 olfactory nerves ; 2, 3, 4, nerves of the veil, 2 sends a branch to the channel of the mouth 

 and 4 one to the tentacular process on the under side of the veil ; 5, 6, nerves to the skin on 

 the sides of the body; 7, genital nerve; 8, pallial nerves; 9, 10, 11, pedial nerves; 12, 13, 

 buccal nerves; 14, lingual nerve; 15, nerves to the salivary glands; 16, nerves to the root 

 of the oesophagus ; 17, oesophageal nerves. 



10. Inside view of the jaw of T. plebeia : — a, point of articulation ; b, cutting edge ; c, denticulated 



belt. 



11 . A portion of the jaw of the same more highly magnified :— a, cutting edge ; b, denticulated belt. 



12. Under view of a portion of the oesophageal ganglia of the same : — a, cerebroid ganglion ; b, 



branchial ; c, pedial ; d, commissures uniting the pedial to the cerebroid and branchial 

 ganglia ; e, auditory capsule. 



