844 THE PALEONTOLOGY OF MINNESOTA. 
[Bellerophoutacea, 
Suborder BELLEROPHONTACKEA. 
This suborder is proposed for the reception of a type of Gastropoda that seems 
to be totally extinct. The elements to be comprised in it have heretofore been 
referred partly to the prosobranchiate order Pectinibranchiata, some to the 
Heteropoda, and others to the Pteropoda. They are all symmetrical shells and in 
this respect agree with the Patellacea. We believe that they are either descendants 
of the same unknown stock from which that suborder was derived, or that they 
represent an early offshoot from it, differing in the strongly involute (instead of 
patelliform) character of their shells. From recent Heteropoda they differ in having 
a stronger shell and in their habits, which evidently were litoral and not pelagic. 
Systematists have experienced great difficulties in assigning this well-marked 
group of shells to its proper place in nature. Montfort, who was the first to attempt 
it, originally considered his Bellerophon as a cephalopod because he believed it to 
possess a number of septa pierced by a siphuncle. Although the total absence of 
anything like septa was soon demonstrated, Montfort’s view was still maintained 
in the modified form necessitated by the monothalamous character of the shell. 
Blainville placed Bellerophon with the Ophisthobranchiata, but received very little 
support for his view. Not so however with the idea first advanced by Deshayes 
that these shells were Heteropoda. This view seemed to be so well established by 
the external resemblance of certain bellerophontids to the recent genus Atlanta 
that it became very popular. But it also has almost disappeared from modern 
literature. 
The position to which they are now almost universally assigned is among 
the pectinibranchiate order of the prosobranchiate Gastropoda. This arrangement 
was inaugurated by De Koninck in 1848, when he drew attention to certain similar- 
ities existing between the shells of Bellerophon and Emarginula. His view was 
adopted by Pictet and Geinitz, but its general adoption was interfered with in’ 
1866, when Meek seemed to prove that their affinities were even nearer Pleurotomaria 
and Haliotis. Since this date Meek’s view of the natural position of this group of 
symmetrical involute shells has gradually gained many supporters, so that now it 
may be said to be the one that is generally accepted. 
In our opinion the systematic position of the Bellerophontacea is at least approx- 
imately determined. All three of the views now current, Deshayes’, De Koninck’s, 
and Meek’s, perhaps contain an element of truth; the second because Hmarginula is 
either a direct descendant of the ancient type under consideration, or a reversion 
from the pleurotomarian type; the third because the Pleurotomariide probably 
sprang from the same ancestral stock; and the first because there are good reasons 
