G9 



Explanation of tug Plates. 



Reference Letters used in the Plates. 



Note. — The letters d — u in Figs. V^b ;ind 13c refer to the minute 

 muscles of the odontophore, and are not included here. 



A. = Thin brown external layer 



of shell. 



A.C. = Anterior cartilage of 

 odontophore. 



A.-D. Lobe = Autero-dorsal lobe 

 of right kidney. 



A.-L.C. = Antero-lateral car- 

 tilage of odontophore. 



An. C. = Anal cells. 



Ant. Ao. = Anterior aorta. 



Ap. D. = Apical disc. 



B. = Thickmiddlelayer of shell. 

 («) Outer part traversed by 



branching canals. 

 (b) Clear inner part. 

 B.C. = Buccal cavity. 

 B]}. = Blastopore, 

 Buc. — Buccal commissure. 

 Buc.D. = Duct of buccal gland'. 

 Buc.G. = Buccal ganglion. 

 Buc.Gl. = Buccal glands. 



C. = Internal laminated layer of 



shell. 

 Cer. = Cerebral ganglion. 

 Cer.C. = Cerebral commissure. 

 Cil.R. = Pre-blastoporal ciliated 



ring which bejouics proto- 



troch. 



C.-Fed. = Cerebro-pedal con- 

 nective. 



C.-Pl. = Cerebro-pleural con- 

 nective. 



D.F.G. = Dorsal fold of gullet 

 wall. 



D.R.P. = Duct of hepato- 

 pancreas. 



D.P. = Dorsal palatal plate. 



D.Pal.Gl. = Dorsal pallial gland- 

 tissue. 



Ect. = Ectoderm. 



E.-M. = Endo-mesoderm. 



Ep. F. = Epithelial fold. 



Fl. = Flap of lateral (" epipo- 

 dial ") streak. 



F.li. = Foot rudiments (meso- 

 blastic). 



G.-l. = Gland tubules of lateral 

 (" epipodial ") streak, 



G.M.T. = Greater pallial ten- 

 tacle. 



Cr.il/. V. = Great pallial vein. 



Go. = Gonad. 



G.V. = Veinlet from pallial 

 gill. 



H. = Head. 



H.-P. — Hepato-pancrcas. 



