118 
body-whorl, which does not become free at the aperture. A distinct columella is present, and 
this has a peculiar twisted form or is spirally grooved. No umbilicus. Outer lip thin. 
The typical species of Strophostylus are recognised by their thin shell, commonly ex- 
panded round or oval aperture, surface with simply concentric lines, and twisted columella. 
The last character, however, is one which is very rarely available, and it may, therefore, be 
left out of consideration. The surface ornamentation is likewise not constant, for whilst con- 
sisting in the typical species of transverse strize alone, Hall has described species with longi- 
tudinal or revolving striz in addition, and the Strophostylus? cancellatus of Meek and Wor 
then has a regularly cancellated surface. In these cases, the shell comes closely to resemble 
Cyclonema and some species of Holopea, and, if the columella can not be observed, the determi- 
nation must rest upon the general form of the shell, which has a depressed or slightly elevated 
spire and a greatly expanded body-whorl and aperture in Strophostylus, whereas in the two 
last-mentioned genera the shell is more elevated and turbinate and the body-whorl is only 
moderately large. It is quite possible that these differences may often prove deceptive, but 
in the numerous fossil Gasteropods in which the mouth can not be observed, it is difficult to 
point to any other characters by which a generic determination may be effected. 
In the Corniferous Limestone of Ontario occur two or three species of Gasteropods which 
have the general form of Strophostylus with the cancellated surface of Cyclonema or Holopea 
(in part). The true affinities of these, owing to their imperfect preservation, can not be made 
out; but, in accordance with the considerations above brought forward, I shall in the mean- 
while refer them provisionally to Strophostylus. I have not been able to identify any of these 
with previously-recorded species, and have, therefore, b:en compelled reluctantly to describe 
them as new. As many of the descriptions of the known species are, however, very incom- 
plete, it is quite possible that they are not really new. 
_ 145. SrropHostyLus? suB-@LoBosuS (Nicholson). 
(Plate II., Fig, 3). 
Shell globose, thick, with a depressed spire which is hardly elevated above the upper 
surface of the body-whorl, except close to the aperture. Volutions three, very rapidly increas- 
ing in size, conyex, the body-whorl enormously expanded and somewhat flattened on its upper 
surface. Height one-third less than the width. Sutures not canaliculated, and hardly 
marked at all except between the body-whorl and the spire near the aperture. Aperture 
large, nearly circular, the outer lip meeting the volution above at considerably less than a 
right angle, and not extending any further forward than the margin of the aperture below. 
Outer lip apparently not reflected; inner lip callous; apparently no umbilicus, Surface 
with numerous revolving thread-like striw, of which five occupy the space of one line, and 
which are crossed by elevated thread-like transverse strize, which are directed obliquely back- 
wards, and of which about three occupy the space of one line, thus giving rise to a system of 
oblong cancelli. 
Height of specimen fourteen lines ; width, twenty-two lines; height of aperture, thirteen 
lines ; width of aperture, thirteen lines. 
From S. globosus (Hall), the present species is separated by its larger dimensions, its non- 
canaliculated suture, and its much more distinct cancellation. From Strophostylus ? cancellatus 
of Meek and Worthen, it is separated by the fact that the outer lip does not meet the 
volution above at a right angle, and is not prolonged further forward than the lower margin of 
. aperture, whilst the shell appears to be much larger and more globose, and the cancellation 
is more distinct and pronounced, / 
Locality and Formation.—Corniferous Limestone, Port Colborne. 
146. SrropHosTYLUs? ovatus (Nicholson). 
(Plate II., Fig. 10). 
Shell transversely elongated or ovoid, the height being to the width as three to five. 
Spire small, moderately elevated ; volutions three, regularly convex ; the sutures apparently 
linear, and not canaliculated ; the body-whorl ventricose and especially dilated near the 
