Autodetus uli<1 Paramorphic sin lis. — Clarke, 
331 
Fig. 8. Lateral view of A utodetus beecheri. Fig. 
9. An external cast preserving at the apex the 
tilling of the primary whorls, x :{. Lower Oris- 
kany, Becraft's Mt., N. Y. 
therein its inception. Had the early mode of growth been 
perpetuated, a planorbii'orm but sinistral shell attached by 
the upper margin of 
each whorl, would have 
resulted, or such a shell 
as is often presented by 
Spirorbis, where the sud- 
den deviation in curva- 
ture does not occur. 
The same deflection in 
curvature which characterizes the later growth-stages of mosl 
forms of Spirorbis was undoubtedly, in Autodetus, an efficient 
cause in producing the conical form of the shell in post-in- 
fantine stages. 
The sutures rarely leave any trace upon the exterior, though 
when there has been a slight compression of the shell the 
course of the whorls may be traced from without, by a low 
spiral undulation. 
The formation of a columella is a peculiar feature of this 
genus, due to close coiling and the same hypertrophic exuda- 
tion of testaceous matter which has produced the thickened 
cicatrix and outer walls and has obliterated the sutures. 
In 1865 Billings described* from the base of the Ordovician 
((Quebec group) a conical, sinistral shell, to which he applied 
the name Clisiospira (C.curiosa). There is little known of 
the species, save that it is not attached at its apex, that the 
first two or three volutions of the spiral are clearly defined 
by an external suture, and that the body whorl is broadly ex- 
panded and trumpet-shaped. Billings further st;ites that "the 
cavity occupied by the animal appears to be, at least in the 
lower part, not spirally coiled, but straight and central, with 
the lip spread out all around." Two additional species, which 
are referred to Clisiospira by Whitfield, C. occidentalism, from 
from the Trenton limestone, and C. lirataA from the Calcifer- 
ous fauna, afford little additional information in regard to 
the internal structure, except that in the former the suture is. 
on the internal cast, clearly apparent, even to the aperture. 
•Palaeozoic Fossils, vol. i. pi'. 186, 120. 
|< Icnlntry < if Wiscmisi ii. vol. iv, p. 222, pi. ."). fig. 21, 1884. 
^Bulletin American Museum Natural History, vol. i. p. 308, pi. 25, 
figs. Ki. 1 ?. 1886. 
