356 KANSAS UNIVERSITY SCIENCE BULLETIN. 
apparent. The pleurocentral-neurocentral suture is apparent 
in four vertebree. 
There is but a single pleurocentrum preserved complete. 
This shows the form of the attached neurocentrum and chev- 
ron, which corresponds to the hypocentrum pleurale, according 
to Fritsch. These structures are shown in the drawing, figure 
1, plate 9. The pleurocentrum is flattened laterally, with a 
rather large canal for the notochord. Its sides are marked 
with four longitudinal grooves. Surfaces for the attachment 
of ribs are not present, and for this reason, as well as the 
presence of chevrons, the vertebre are supposed to be caudals. 
As such, they represent an animal of some three or four feet 
in length. It was the giant of the Mazon Creek Amphibia. 
Attached to the upper side of the pleurocentrum by a sutural 
union occurs the neurocentrum. The neural arch is quite large 
and is oval in outline, although somewhat constricted at the 
tip. The spine of the neurocentrum is rather long and broad 
at its base, measuring 12 mm. across the anterior zygapophy- 
sis. The nerocentrum is laterally flattened and ends in 
a rather acute and somewhat rugose point. It was probably 
tipped with cartilage. The anterior zygapophysis occurs well 
down on the neurocentrum; its lower edge being five milli- 
meters from the suture separating the pleurocentrum and the 
neurocentrum. The posterior zygapophysis occurs quite high 
up on the neurocentrum, and lies at a distance of 15 mm. from 
the pleuro-neurocentral suture, thus indicating an extreme 
posterior inclination of the neural spine. The posterior 
zygapophysis of the best-preserved vertebra is separated from 
its mate, the anterior zygapophysis, on the next succeeding 
vertebra, by a space of five millimeters. 
The ventral surface of the pleurocentrum bears a structure 
which is without doubt a chevron, although the character of 
the opening can not be determined. It is elongated and is 
united by a broad base to the pleurocentrum. Its union is by 
a clearly defined suture, which is apparent on three vertebre. 
The condition represented by the specimen represents almost 
exactly the condition figured by Cope for the caudal region 
. of Cricotus crassidiscus Cope’. 
The intercentrum of the present form is fully as large as 
the pleurocentrum. The significance of this has already been 
1. Cope, E. D., 1890. Trans. Amer. Phil. Soc., vol. xvi, p. 246. 
