EXTINCT AMPHIBIA OF NORTH AMERICA 49 
the specimen is the impression of the lateral line system, which is 
clearly evident as two dark lines on the impression of the fleshy part 
of the tail. The sense organs are represented by two longitudinal 
rows of pigmented scales, one beginning at the tip of the tail, the other 
Fic. 6.—Impression of the tail of Micrerpeton caudatum showing the arrangement 
of the lateral line sense organs and the position of the vertebral column. D-=dorsal 
lateral line; M-=median lateral line; F=femur; S=scales; V=vertebral column. 
X5- 
taking its origin from the median line somewhat further forward. I 
am indebted to Dr. K. Takahashi for calling my attention to the simi- 
larity of this arrangement to that found in the modern Necturus. 
The arrangement and disposition of the lines containing the sense 
pL oS D M 
Liege 
Lees: 
04° og OO 2°00? eco 
S 2$40A\0 5, 0° EZ lee bo,gooee oboocecd > 
208 \90? ° o al “atx 
Co 2 Lt 
\ oc EBS 26028590 . 
oo! = e°° o 
Y Po? 2cogoogs Cy, ae es 
Fic. 7.—Outline of a young larva of Necturus showing the position of the lateral 
line system. D=dorsal lateral line; H =hyomandibular sense organs; I =infraorbital 
sense organs; M =median lateral line; R=mandibular sense organs; V = ventral lateral 
line; X=sense organs supplied by branches from the glossopharyngeal and vagus 
nerves; Y=the position of the vertebral column. Modified after Platt. Enlarged. 
organs is practically the same in the two forms (Figs. 6, 7). The 
median lateral line takes its origin from the extreme tip of the tail and 
is continued to the base where the impression is broken. The dorsal 
lateral line has its origin rather abruptly from the median lateral 
line at a distance of six millimeters from the tip of the tail. The 
