MAXILLARY AND VOMER BONES OF POLYPTERUS 385 
The primary upper lip is apparently represented in the so- 
called median lateral-fold of Fuchs’s descriptions. This fold is 
not described by him in embryos of Chelone, but it is in em- 
bryos of certain others of the Sauria, there lying lateral to 
the lateral lip of the nasal groove, the so-called choanate fold, 
between that fold and the maxillary teeth, and where there are 
palatopterygoid teeth, as in Tropidonotus, they apparently de- 
velop immediately internal to this fold. This fold thus certainly 
represents the primary upper lip,and is the homologue of the 
maxillary breathing-valve of fishes. In mammals it is said by 
Fuchs to become the secondary palate, that palate thus being 
represented in the maxillary breathing-valve of fishes, as | 
suggested in my earlier work on Polypterus (Allis, ’00). 
SUMMARY 
There are thus, in recent teleostoman fishes, several distinctly 
different types of secondary dental arcade in the upper jaw. 
In one of these types the maxillary and premaxillary each has 
two components, one dental and the other dermal, the latter 
component being formed by bones developed in relation to the 
laterosensory canals. The teeth on each of these bones ap- 
parently issue approximately along the line of the primary upper 
lip, the maxillary teeth lying internal to the labial fold and 
hence definitely internal to both upper labial cartilages. This 
dental arcade is found in Polypterus, and also in Macropoma, 
one of the fossil Crossopterygii, and it apparently corresponds 
to the dental arcade of the Mammalia. 
A second type is found in Conger, the premaxillary here being 
represented by teeth that have fused with the dermal ethmoid, 
and the maxillary corresponding either to the maxillary and post- 
maxillary bones of the fossil Macropoma, or, more probably, 
being a bone developed in relation to teeth that correspond to the 
inner row of teeth on the so-called maxillary chain of canal- 
bones of Lepidosteus, those teeth having apparently been pri- 
marily developed in relation to tissues that represent the posterior 
upper labial cartilage. 
