EXTINCT AMPHIBIA OF NORTH AMERICA 51 
So far as I am aware the species above described is the earliest 
geological evidence of the Branchiosauria since the earliest forms 
known from Europe are from the Stephanian (Upper Carboniferous). 
The species is also the only true branchiosaurian known from North 
America as stated above. The presence of this form in America is of 
considerable interest in the bearing it has on the distribution and 
migration of the Paleozoic animals. It is a great distance from Europe 
where the other Branchiosauria are found, to America and it must 
have taken an immense length of time for such slow-moving creatures 
as the Amphibia to have migrated this distance. Whether the 
migration took place after the development of the branchiosaurian 
type or whether the type was evolved in the two places is an open 
question and must be settled by future research. It is possible that 
it was the piscian ancestors of the Amphibia which migrated across 
the seas and began the amphibian phase of their development 
independently in the two continents. 
MEASUREMENTS OF THE SPECIMEN OF Micrerpeton caudatum MoovIE 
Entirelengthyoframimiall ey igcn ts hes dus eye ne em Spa 49 
Wwenethiot mead um=medianeline. se ac ect cles 6.5 
Nidthvotwheadsatiposteriom borders) 42. esac ne eng 8 
Wenothpottorbithsrre ome ay ac earns ont: EAN needa aan teste 2)..5 
NWAGIEMROL OT Di tep crs yee ey EN Gee ee cst cents oie Seer 2 
ititeronbitalksmace piety eet inet oceans ey dean 2 
Wenpthvotgvertebralcolumim wee ih teem eae scenes) deca 33 
Wengthcottsinglevertebraunedorsalseries.>. 2322222: Ong 
Length of trunk:from base of skull to'sacrum.. 42 ...4..%. +. 22 
Bema, thw @ etl lo ecm meres re cast itis oka. tote Nene cae tag tas 1,5 
NeenothWotiscapulace asain. Sisomi: sa A stingers Sct 3 
Wivdithvotyclava cle siaaverxa mtn tsk eens aye ear e 2 
Vie Seyee at cope Veubban Vex qUISI Galera. ke pepe cne Nieto erent ene Perse fe 
MWemotheo i lnm au pice eit Suk Be anc oes he. cha nelt Soar ats cS 
MBemcihwoimie min sey een earth gg. cies inate eree rh way ge aera 2 
ene thyots tilly valve Suet enki acyl hat NON Ae citable 1755) 
enothyottarlmmpressiombe sees sat scares fi cy aire rece tencis sis ee 2Ts5 
WadithyotstaileimapressionyatyoaSerr. vase segs oes pete 4 
The Microsauria are represented in the Carboniferous of North 
America by numerous forms usually with well-developed dermal 
plates and almost always with the ventral scutellation. They ranged 
