594 TransacUoiis. 



13. Sarasin, P. and F. : " Die Sdsswasser Molluskeu v. Celebes," Wies- 

 baden. (Abstracted in Zool. Jahresbericlit, 1898, p. 37.) 



14. Sedgwick : " Text-book of Zoology," pt. 1 — Mollusca. 



15. Rawitz : Internation. Monatsclir. Anat. Pliys., xv, p. 199. (Ab- 

 stracted in Zool. Jahresbericht, 1898, p. 29.) 



16. Pelseneer : Lankester's " A Treatise on Zoology." pt. 5 — ^Mollusca. 



EXPLANATION OF PLATES XXVili. XXIX. 

 Plate XXViII. 



Fig. 1. Side view of Siphonaria obliquata ; natural size, a, apex of shell ; hw, body- 

 wall ; h, head ; ms, muscular swelling of body-wall forming valve to close 

 respiratory orifice ; r, respiratory orifice ; sn, siphonal notch ; s, shell. 



Fig. 2. Ventral view of 8. obliquata ; natural size (from a contracted spirit specimen). 

 /, foot ; gj), genital pore ; h, head ; m, mouth ; ms, muscular swelling of 

 body- wall forming a valve to close the respiratory orifice ; me, free edge of 

 mantle ; r, respiratory orifice ; s, shell. 



Fig. 3. Ventral view of 8. obliquata ; natui'al size (from a large specimen well distended). 

 II, left lobe of head ; pg, pedal gland ; p, pore of pedal gland opening on to 

 l^ropodium ; rl, right lobe of head. Other letters as in fig. 2. 



Fig. 4. Anterior view of *S'. obliquata. Same specimen as represented in fig. 3 ; natural 

 size, a, apex of shell ; e, eye ; h, head ; rl, right lobe of head. 



Fig. 5. Shell of <S'. obliquata ; dorsal view ; natural size, a, apex ; sn, siphonal notch. 



Fig. 0. Alimentary system ; side view ; digestive gland removed ; X 2. a, anus ; 

 bm., buccal mass ; d<j, remains of left part of digestive gland, showing the 

 two ducts entering the stomach close together ; dg', remains of right part 

 of digestive gland ; fb, floor of body-cavity; /, foot; /, intestine; n, nerve- 

 collar ; oe, oesophagus ; r, rectum ; sg, salivary gland ; st, stomach. 



Fig. 7. Dorsal surface of S. obliquata ; shell removed ; x 2. a, auricle ; ar.v, anterior 

 renal vein; a\.v., an afferent vessel of lung; af.pul.v, afferent pulmonary 

 vein ; af.br.v, afferent branchial vein ; ef.v, an efferent vessel of lung ; 

 ef.pul.v, efferent pulmonary vein; ef.br. i\ efferent branchial vessel; g, gill; 

 k, kidney ; I, lung ; me, mantle-edge ; pm, pallial muscles ; pcd, peri- 

 cardium ; prv, posterior renal vein ; pv, pallial vessels ; t", ventricle. 



Plate XXIX. 



Fig. 1. Sholl of S. obliquata ; ventral view, mt, muscle impressions and tracts, show- 

 ing successive position of the muscles as the animal grows ; sn, siphonal 

 notch. 



Fig. 2. Dorsal view of iS'. obliquata, with pallial chamber opened and mantle turned 

 to the left; X 2. a, anus; af.br.v, afferent branchial vein; ef.pul.v, 

 efferent pulmonary vein ; g, gill ; dk, dorsal part of kidney ; /, lung ; ms,. 

 muscle-fibres of floor of pallial chamber ; me, free mantle-edge ; pm, pallial 

 muscles ; rp, renal papilla ; r', respiratory orifice leading into pallial 

 chamber; vk, ventral part of kidney; ef.br. i; efferent branchial vein; ar.r. 

 anterior renal vein ; af.pul.v, afferent pulmonary vein. 



Fig. 3. Body-cavity opened by cutting through the floor of the pallial chamber, show- 

 ing internal organs in situ ; x 2. a, anus ; bm, buccal mass ; bw. body- 

 wall pinned aside ; cd, common duct ; dg, digestive gland ; hg, hermaphro- 

 dite gland ; /, intestine ; oe, oesophagus ; p, penis ; pro, prostate ; r, 

 rectum ; sg, salivary gland ; st, stomach ; sth, spermotheca ; stM, spermo- 

 theca duct. 



