1228 MR. F. R. WELLS ON THE MORPHOLOGY OP THE 



4. Until the 20 mm. stage is reached, the brain is in no place 



roofed over. 



5. The Trabeculse Oranii disappear between 20 mm, and 30 mm., 



leaving a median process, which does not join the posterior 

 part of the skull. 



6. The quadrate appears by a constriction in the hy ©mandibular 



mass. 



7. The symplectic appears as a thin pointed process from beneath 



this mass. 



8. Articulations of this mass with the cranium and with Meckel's 



cartilage appear at 10 mm. and 26 mm. respectively. 



9. Considerable ossification is taking place at 30 mm. 



7. List of Abreviations used in the Illustrations. 



Br Branchial arches. 



C.H Ceratohyal. 



E.B Epiphysial bar. 



Eth Ethmoid plate. 



Fletc Foramen of I(etc.) nerve. 



H.M Hyomandibular. 



Mk Meckel's cartilage. 



NaS Nasal septum. 



N.O. Notochord. 



P.F Pectoral fin. 



P.G Pectoral girdle. 



P.O Post -orbital process. 



PP Palato-pterygoid cartilage. 



Qu Quadrate. 



R Rostrum. 



RaP Retro-articular process. 



StyH. Stylo-hyoid. 



Sy Symplectic. 



T.C Trabeculse Cranii. 



8. Bibliography. 



1. Balfour, F. M. — Monograph on the Development of Elasmo- 



branch Fishes. 1878. 



2. BoKER, H. — Der Schadel von Salmo solar etc. Anat. Hefte, 



i. p. 49, 1913. 



3. Bridge, T. W. — Cranial Osteology of Amia calva. Journ. 



Anat. & Phys. 1877. 



4. Brooks, H. J,. — On the Osteology of the Haddock. Proc. 



Roy. Dublin Soc. 1883. 



5. Fage, L. — Report of the Danish Oceanographical Expedition : 



Clupeidse. 1920. 



6. Huxley, T. H. — On the Theory of the Vertebrate Skull. 



Proc. Roy. Soc. 1868. 



