No. 2.] LATERAL LINE IN EXTINCT AMPHIBIA. 537 
SUMMARY. 
1. There are present on the skulls of the extinct Amphibia 
seven distinct lateral line canals, all more or less connected. 
2. These canals may be partly homologized with those of 
fishes. They may be termed: the anterior commissure, 
homologous with the same canal in fishes; the antorbital com- 
missure, homologous with the similarly placed canal in fishes; 
the infraorbital canal, homologous with that of fishes; the 
supraorbital canal, homologous with that of fishes; the tem- 
poral canal, homologous with the posterior portion of the in- 
fraorbital canal of fishes; the jugal canal, homologous with the 
operculo-mandibular (?) and the posterior portion of the 
infraorbital (?) canal of fishes; and the occipital cross-com- 
missure, homologous with the supra-temporal cross-commis- 
sure of fishes. 
3. The lateral system has been discovered in four of the 
five suborders of the Stegocephala. 
4. The Branchiosauria have a type of lateral line on the 
tail which is similar to that on the tail of the modern Nec- 
turus. The branchiosaurian skull is not grooved by the lat- 
eral line canals. 
5. In the Microsauria, so far as known, the system of the 
lateral line canals is well developed. The occipital cross- 
commissure is present on the skulls of at least two genera. 
6. In the Temnospondylia the lateral line canals are of a 
peculiar type, especially so in the form described, Eryops. 
The occipital cross-commissure is well developed. 
7. The Stereospondylia always have the lateral line canals 
well developed. This character is an indication of age and 
specialization. The occipital cross-commissure is present in 
a single species of the Stereospondylia. 
8. The so-called squamosal bone in the skull of the Stego- 
cephala is really that element and not the supratemporal. 
9g. The following elements of the stegocephalan cranium 
‘are homologous with the same elements in fishes: the pre- 
maxille, maxille, nasals, frontals, prefrontals, parietals, 
squamosals, and postfrontals. The epiotics and supraocci- 
