69] THE SKULL OF AM lURUS— KINDRED 69 



According to Allis (1898), the lacrimal of Amia is the homologue of the 

 first suborbital of Amiurus. He regarded the adnasal of Amiurus as described 

 by McMurrich (lacrimal, Auct.) as the homologue of the antorbital of 

 Amia, justifying his statement by saying that CoUinge says that many authors 

 call the bone by that name. Since this bone in Amiurus contains the anterior 

 end of the suborbital lateral hne canal, I have called it the lacrimal, and it is 

 possible that the long anterior lateral process may be the homologue of the 

 antorbital of Amia. Merely because there are six infraorbitals in Amiurus and 

 Amia, counting the lacrimal in the latter, but not in the former, it does not 

 follow that the members of the series are numerically homologous from the 

 anterior to the posterior end. The criterion for homology rests upon the 

 relation of the bone to the nasal capsule and the part of the lateral line that it 

 contains. 



The vomer. This bone, broad, fiat, and unpaired, lies near the anterior 

 end of the ventral surface of the cranium. It is entirely superficial to the 

 bones which invest the chondrocranium in this region and is covered by the 

 skin of the roof of the mouth (Fig. 6). As McMurrich (1884b) said, the bone 

 is nail-shaped, the head of the nail is represented by the broad anterior portion 

 and the shaft by the posterior spicules. It lacks the anterior extension com- 

 mon to the vomer of most teleosts, and is limited in front by the supraetlimoid. 

 The serrate line of interdigitation between these two bones extends as far 

 laterally on each side as the ventral end of the supraethmoid-ectethmoid 

 interdigitation. The vomer is here separated from the margin of the descending 

 ectethmoid by a cartilaginous plate which is continuous with the palatine 

 articular surface. Postero-laterally each side of the vomer interdigitates with 

 the anterior edge of the ventral portion of the ectethmoids. Internal to these 

 edges the several spicules mentioned above extend posteriorly in a series of 

 grooves on the ventral face of the parasphenoid. The bone does not articulate 

 with the premaxillaries and it is firmly united with the parasphenoid. The 

 ventral ossification of the supraethmoid extends beneath it, separating the 

 anterior part from the chondrocranium, while the anterior end of the para- 

 sphenoid cuts it off behind from the orbitosphenoid (Fig. 7). The bone itself 

 is very thin and some of the fascia for muscle fibres of the entopterygoid muscle 

 are attached to the postero-dorsal margins. It has no teeth and none are 

 developed in the roof of the mouth below it. The development of the bone 

 has been described earlier in the paper. 



Since Cuvier compared this bone in the fishes to the vomer of man, it has 

 borne this name, although many arguments have been advanced for and 

 against this view which I will not attempt to discuss here. As it is one of the 

 most evident bones on the anterior ventral surface of the skull in all teleosts, 

 there has been no confusion in describing its topography. In some of the 

 lower teleosts — Scomber, Salmo, and the Loricati are among the best known 



