F. B. Meek on Acteonide. 85 
forms curiously simulating types often not then in existence, but 
subsequently introduced even within widely separated families. 
Thus in the genus Cylindrites which first appeared during the 
Jurassic period, we observe forms closely resembling the more 
modern genus Oliva, while others shade off towards Acteon and 
Bulla. In Acteonella, we have a type nearly resembling the 
Tecent genus Volvula of the family Cylichnide ; and in the Ju- 
i¢ genus Huconacteon, which is connected (in a family sense) 
through the sub-genus Conacteon, with Acteonina, there is pre- 
sented a striking archetypal representation of the more recently 
Introduced genus Conus. In Globiconcha and Bullopsis, the genus 
Bulla is again represented; while Cinulia mimics, as it were, 
certain groups of the Auriculide.’ Again, if we admit into the 
family under consideration the genera Pterodonta, Tubifer, and 
Soleniscus, which seem to have some relations in this direction, 
acte@on and Conacteon to belong to the genus Conus. It was not 
therefore until @Orbigny and others had ascertained from the 
the aperture effuse below and notched above, as well as in hay- 
ing the whorls all alike extremely thin,—that the true relations 
of these shells were understood Differences of nearly equal 
ae ence have been discovered also between the other forms 
and the several modern groups to which they were at first sup- 
Posed to belong, ae 
The descriptions of the family Acteonide generally given in 
the Works on recent Conchology, although correct so far as the 
*Xisting genera are concerned, do not convey a clear idea of the 
Whole group, as developed through all the various epochs of the 
, Since its first introduction during the Carboniferous (or 
genus pind iyi the species were at first referred, by the best paleontologists, to the 
Male, is but just to mention here that Deslongchamps, at the same time that he re- 
ern 
é 
1 
gen In their ext ness, and com respec 
Bulla, (Mem. Bon Lick ae Normandie, vol. vii, p. 147). It was d’Orbigny, how- 
Who first pointed out (so far as known to the writer) that they differ in thick- 
the outa the true Cones, mainly in having all the whorls very thin; ae 
Suter whorl is thick, and the inner ones absorbed away to a mere film of shell. 
