71 



7?.7?.P. = Renal aperture of reno- 



pericardial canal of right 



kidney. 

 R.S. = lladular sac. 

 S.C. = Sense cell of eye. 

 Sec F.Cr. — Radial secondary 



folds on the transverse crop 



folds. 

 Scc.G. = Secondary or pallial gills. 

 S.L.P. = Sub-lingual pouch. 

 S.AI. = Shell muscle. 

 S.-B. Lobe. = Sub-rectal lobe of 



right kidney. 

 S.B.M. = Sub-radularmcmlirane. 

 St. = Stomach. 



Sl.Gr. = Groove in stomach-wall. 

 Siib-Ep.N.L. ^ Sub-epithelial 



nervous layer. 

 Siib-Oes.C. = Sub-oesophageal 



connective of visceral loop. 

 Hup.-Int. = Supra - intestinal 



ganglion of visceral loop. 

 S.Z. = Sensory zone of mantle 



epithelium. 

 T. = Tentacle. 

 T.N. = Tentacular nerve. 



r. Visceral loop. 



I'ac.E. = Vacuolated epithelium 



beneath lateral streak. 

 V.F.G. = Ventral fold of gullet. 

 V.G. — Visceral ganglion. 

 V.ll. = Visceral hump. 

 ]' .Tj.C. = Ventro-lateral cartilage 



of the odontophoru. 

 V.-l.F. = Ventro-lateral folds of 



wall of rectum. 

 17. = Veinlet from mantle edge. 

 V.-Lobe. = Ventral lobe of right 



kidney. 

 r». = Ventricle. 

 )'.,S7. = Valve hindering flow of 



secretion of hepato-pancreas 



into anterior part of gut. 

 X is the point of connection 



between Int. 1 (Fig. lOrt) and 



Int. 2 (Fig. 106). 

 Y. is the point at which the 



stomach folds on itself 



(Fig. lOry). 

 Z. is the anas-tomosis between 



the posterior pallial nerves 



of the two sides. 



The terms rigJtf and left are always used to signify post-torsioiial 

 relations unless otherwise specified. 



Plate I. 



Pig. 1. Extreme forms of shell of I'atclhi viihjatti. ]'\'om 

 specimens collected in the Goiiliot Caves, Sark. 



Fig. 2. Section thi-ough the shell. A Thin hrown external 

 layer, li Thick middle layer: [n) outer part 

 traversed by branching canals ; {h) clear inner 

 part. C Internal laminated layer. x 15. 



Fig. 3. • The animal in its shell — Ventral surface. //. = Head. 



Fig. 4. Dorsal view to show positions of organs. The 

 pigment layer of t!ie nuuitle has been rul)hed off 



