1893.] Geology and Paleontology. 35 
area under consideration are all Paleozoic, and include representatives 
of all the larger subdivisions of that system. A columnar section of 
the strata exposed east of Browntown Valley gives the Cambrian rocks 
an average thickness of 7550 feet; the Silurian, 5935 feet; the Devon- 
ian, 180 feet; and the Carboniferous, 2175 feet. The formation names 
are all new, being purely geographic and local. It is questionable if 
the making of new names is necessary in regions contiguous to those 
with similar formations whose names have been generally adopted. 
The reason advanced, “ to avoid all remote correlations,” does not seem 
sufficient to warrant such innovations. 
The report is accompanied by an excellent Geological map which 
shows a structure section through Northeastern Alabama. 
The Mesosauria of South Africa.—Paleontologists are indebted 
to Prof. H. G. Seeley for a detailed description of the Mesosauria of 
South Africa, and an exact statement of the relations of Mesosaurus 
with Stereosternum. 
For many years the genus Mesosaurus has been evidenced by a 
single fossil from Griqualand, South Africa, described by Gervais in 
1865 under the name Mesosaurus tenuidens. In 1878 four specimens 
from the shale at the margin of the Kimberley Diamond field were 
obtained by Mr. G. H. Lee, and deposited in the British Museum. They 
show that Mesosaurus was a long-tailed reptile, with hind limbs well 
developed. Mr. Seeley found it impossible to refer the Kimberley speci- 
mens to M. tenuidens, and described them under the name M. pleuro- 
gaster. The well-developed abdominal ribs, formed of flattened 
plates, give this species its most distinctive feature. 
A second specimen of M. tenuidens found in the district of Albania 
by David Arnold, preserved in the Cape Town Museum, shows the 
ventral aspect of the anterior part of the skeleton. There are some 
differences between this specimen and the type, but Mr. Seeley does 
not consider them important enough to prove specific distinction. 
Another specimen of the same genus, from near Burghersdorf, is in 
the Albany Museum at Grahamstown. It shows the dorsal aspect of 
dorsal vertebre and ribs. It indicates a new species, but there is no 
character available for its definition except that of relatively stout 
ribs. 
In discussing the relations of Mesosaurus with Stereosternum, 
Mr. Seeley refers to Stereosternum tumidum from Brazil, described 
by Cope in 1886, and figures the shoulder girdle of that species 
to show a pair of wide, thin, crescentic bones in advance of the 
