622 



SAMPSON. 



[Vol. XI. 



REFERENCE LETTERS. 



/ Shell I. 

 // Shell II.i 

 Etc. 

 II ap apophysis of shell II, etc. 

 A anterior. 

 aga region of attachment of the 

 anterior group of pedal mus- 

 cles under IV. 

 al anterior lateral muscle of the 



buccal mass. 

 ao antero-oblique muscle. 

 aox antero-oblique muscle of the 



anterior group. 

 aOi antero-oblique muscle of the 

 posterior group. 

 ac/x or ao'2 antero-oblique muscle (at 

 a low level) of the group next 

 posterior to the group in the 

 section represented. 

 ap apophysis. 

 ba branchial artery. 

 bv branchial vein. 

 bvn branchio-visceral nerve. 

 be body cavity. 



bm a portion of the buccal mass 

 protruded through the mouth. 

 C buccal cartilage. 

 c cushion of muscles between the 



shells. 

 Ci oblique muscles of the cushion 



in the transverse plane. 

 Ci, oblique muscles of the cushion 



in the sagittal plane. 

 ^3 oblique muscles of the cushion 



in the horizontal plane. 

 cl circular muscles in the lip. 

 cr crossed muscle of the buccal 



mass. 

 era region of attachment of this 



muscle. 

 dpr dorsal protractors of the buccal 

 mass. 

 dpra region of attachment of these 

 muscles. 

 dv " dorso-ventral " muscles under 

 I, corresponding to the latero- 



pedal muscles under the other 

 shells. 

 d-c/a region of attachment of these 



muscles. 

 d7/a region of attachment of the 

 inner group of additional 

 dorso-ventral muscles. 

 dv"a region of attachment of the 

 outer group of additional 

 dorso-ventral muscles. 

 g/ gland opening into the oesoph- 

 agus. 

 F foot. 



// horizontal fibres in the trans- 

 verse plane under I. 

 HF head-fold of the foot. 

 Ami horizontal median fibres to the 

 anterior lip. 

 Al horizontal longitudinal muscle 



from VIII to the foot. 

 tm interior mantle muscle. 

 ima region of attachment of this 

 muscle. 

 L lips. 

 // lateral longitudinal muscle of 



the shells. 

 /p latero-pedal muscle. 

 Ipi latero-pedal muscle of the ante- 

 rior group. 

 /P2 latero-pedal muscle of the poste- 

 rior group. 

 Ipr lateral protractor of the buccal 

 mass. 

 Ipra region of attachment of this 

 muscle. 

 Jll mantle. 

 me mantle chamber. 

 md median dorsal muscle of the 



shells. 

 mp medio-pedal muscle. 

 mpi medio-pedal muscle of the ante- 

 rior group. 

 mp2 medio-pedal muscle of the poste- 

 rior group. 

 msi broad muscles of the radula 

 sheath. 



^ The numerals 11 and III have been reversed in Fig. 10. 



