UWfV.rno^"''''^ 
THE 
AMERICAN GEOLOGIST. 
Vol. XX. NOVEINIBER, 1897. No. 5 
ON STREPTELASMA PROFUNDUM (Owen) 
S. CORNICULUM Hall. 
By F. W. Saedeson, University of Minnesota. 
(Plates XVI and XVII.) 
Twelve species of the genus Streptelasmn have been describ- 
ed in America, from the Trenton and Hudson stages and in 
addition three species from the Hudson stage, w^hich have 
been referred to the genus Zaphrentls. It is evident, however, 
upon investigation of several of these species, that they are 
synonyms only. There is apparently but one true species among 
the fifteen. I sa}'- apparently because I have not sufficiently au- 
thentic specimens of some of them to enable me to prove be- 
yond doubt that only one true species is represented among 
the fifteen described as distinct. My collection contains sev- 
eral at least of the proposed species and without exception 
the ascribed distinctions between them, when studied, prove 
to be imaginary or not valid. The one species, S. 2>rof«ndurn 
(Owen), which is known currently as S. cornicuhim Hull, when 
fully investigated shows all the characters which have been 
regarded as the distinctive characters of any one of the other 
fourteen supposed species, and there remains no good reason 
for assuming that more than one species is represented among 
them. If more than one is represented, it is too poorly describ- 
ed for recognition at this time and it is not evident in any of 
the specimens in my possession. Even two more species com- 
