94 



Only casts of the interior of this shell have yet been obtained. Judging- 

 by these the species is provisionally referred to Billings's genus Stra- 

 parollina, though it may prove to be a Pycnomphalus. 



Strapaeollus Hippolyta, Billings. 



Straparollu-s Hippolyta, Billings. .1862. Geol. Surv. Canada, Pal. Foss., vol. I., p. 



160, fig. 144, a-b. 



Gait, E. Billings and John Richardson, 1857, and R. Bell, 1861 ; 

 Elora, T. C. Weston, 1867. This species, also, is still only known from 

 casts of the shell, upon which no trace of the surface markings is 



preserved. 



HoLOPEA, Hall. 



The genus Holopea was referred to the Littorinidse by Salter in 1859,. 

 and by Lindstrom in 1884, but to the Turbinidse by Zittel in 1882. 

 Fischer, in his " Manuel de Conchyliologie," remarks that it is composed 

 of incongruous material, and that it has been circumscribed by Salter and 

 Lindstrom so as to include some small shells apparently near to the 

 Littorinidse. Four species of gasteropoda from the Guelph formation of 

 Ontario have been referred to Holopea, but two of these, viz., H. 

 Guelphensis and H. occidentalis, are known only as casts of the interior of 

 the shell, so that their generic position is still uncertain. 



Holopea Harmonia, Billings. 



Holopea Harmonia, Billings. .1862. Geol. Surv. Canada, Pal. Foss., vol. I., p. 158, 



fig. 142. 



I Gait, John Richardson, 1857 : a single specimen with most of the test 

 preserved on the last volution. 



The salient feature in the type and only known specimen of H. 

 Harmonia, as described by Billings, is the " wide flat band," which is 

 stated to be " equal to a little more than one-third of the whole height of 

 the whorl," around the middle of the last volution. This " band," how- 

 ever, is merely a very faint lateral compression of the centre of the last 

 volution, but in every other respect the shape of the shell is essentially 

 similar to that of the type of H. Oracia. 



