69 



Explanation of the Plates. 



Reference Letters used in the Plates. 



Note. — The letters d — n in Fi.^s. 186 and 13c refer to the minute 

 museles of the odontophore, and arc not ineiuded here. 



A. = Thin l)ro\vn external layer 



of shell. 



A.C. = Anterior cartil ige of 

 odontophore. 



A.-D. Lube = Antero-dor;~al 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. = Thick middle layer of shell. 

 [n) Outer part traversed by 



branching canals. 

 (6) Clear inner part. 

 B.C. = Buccal cavity. 

 Bp. — Blastopore 

 Buc. = Buccal conniiissure. 

 Buc.D. = Duct of buccal gland. 

 Buc.G. = Buccal ganglion. 

 Biic.Gl. = Buccal glands. 



C. = Internal laminated layer of 



shell. 

 Cer. = Cerebral ganglion, 

 Cer.C. = Cerebral commissure. 

 Cil.B. — Pre-blastoporal ciliated 



riijg which bev^omes proto- 



troch. 



C.-Ped. = Cerebro-pedal con- 

 nective. 



C.-Bl. = Cerebro-pleural con- 

 nective. 



D.F.G. = Dorsal fold of gullet 

 wall. 



D.H.P. = Duct of hcpato- 

 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.R. = Foot rudiments (meso- 

 blastic) . 



G.-l. — Gland tubules of lateral 

 (" epipodial ") streak. 



G.M.T. = Greater pallial ten- 

 tacle. 



G.M, V. = Great pallial vein. 



Go. — Gonad. 



G.V. = Veiulet from pallial 

 gill. 



IL = Head. 



H.-P, — Hepato-paiicrtas. 



