70 
homologue of two, and only two of the centres of ossification of the 
bone in man. The third centre of the bone of man, that is the lateral 
postparietal of Polypterus, is said to be found in the Stegocephali as 
a separate bone, the squamosal of ordinary terminology. The lateral 
one of the three posttemporal bones of TRAQuarR’s description of 
Polypterus would seem to be considered by Maccı as the homologue 
of the so-called posterior squamosal of the Stegocephali, when such a 
bone is found , as sometimes occurs. The so-called supratemporal 
bone of the Stegocephali is considered as the homologue of the 
squamous part of the temporal bone of man, and is hence, according 
to Maaai’s determination, the homologue of the operculum of Poly- 
pterus. 
While my work certainly leads me to strongly doubt the correct- 
ness of many of the homologies here proposed by MAccı, I may 
perhaps state that it is not because of his pronounced belief that the 
cranial bones fuse and interfuse with each other in numerous com- 
binations. Gaupp thinks such fusions are much too lightly, and 
usually erroneously, assumed, and he says (No. 16, p. 84) that when- 
ever a particular bone seems missing in any particular anatomical 
region it should not be assumed that it has fused with neighbouring 
bones, unless that assumption is based on positive embryological evid- 
ence; when of course it is no longer an assumption. So far as the 
skull of fishes is concerned, with which I am alone familiar, anatomical 
evidence alone seems to me unquestionably often a good and sufficient 
basis for the assumption. 
As to the incorporation of the extrascapular and suprascapular 
bones of fishes in the skull of mammals, I have always accepted, with- 
out personal investigation or consideration, SAGEMEHL’s several state- 
ments that they form part of the secondary shoulder girdle of the 
animal, and hence that they could not enter into the skull of higher 
animals. 
Palais Carnoles, Menton, 12 April 1889. 
Bibliography. 
1) Auris, Epwarp Preres jr, The Anatomy and Development of the 
Lateral Line System in Amia calva. Journ. Morph., Vol. 2, No. 3, 
April 1889. 
2) — — The Cranial Muscles and Cranial and First Spinal Nerves in 
Amia calva. Ibid., Vol. 12, No. 3, March 1897. 
3) — —, The Morphology of the Petrosal Bone and of the Sphenoidal 
