THE PALEONTOLOGY OF MINNESOTA. 



[Bellerophoutaoea. 



Suborder BELLEROPHONTACEA. 



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 literal 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 1843, 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 Pleurotomana 

 and llaliotis. 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 Emarginula is 

 either a direct descendant of the ancient type under consideration, or a reversion 

 from the pleurotomarian type; the third because the Pleurotomariidai probably 

 sprang from the same ancestral stock; and the first because there are good reasons 



