856 THE PALEONTOLOGY OF MINNESOTA. 
[Bellerophontiidz. 
Permo-Carboniferous of India, W. polita, W. brevisinuata and.W. lata. To these he 
adds three Australian species, Bell. undulatus Dan., Bell. strictus Dan., and Bell. 
micromphalus Morr. 
Moeutia, Waagen, (Pal. Indica, ser. 13, pt. 2, pp. 131, 156; 1880.) General 
appearance of shell as in Bellerophon, from which it differs in having no slit nor slit- 
band, and only a shallow angular emargination in the outer lip. Surface markings 
consisting of lines of growth only. These are broad and strong and cross over the 
dorsum without further interruption than is occasioned by the sharp central bend. 
Only known species, M. regularis Waagen, Permo-Carboniferous of India. 
This and the two preceding genera, Huphemus and Warthia, are of unusual 
interest because we believe they show that in the decline of the family it actually 
retraced its steps by the adoption of primitive characteristics. In other words we 
regard them as atavistic types in which the progressive development of the indi- 
vidual was arrested in the embryo, and in which, because of the failure to develop 
the adult features of their immediate ancestors, certain characters that under 
previous conditions were larval only became permanent. In the Devonian and 
Carboniferous Bellerophontiide the suborder obtained the hight of its development, 
and this was not reached until after the extinction of all the other families. The 
decline, which obviously was very rapid, took place during the time immediately 
preceding the close of the Paleozoic age. Facts like these permit us to assume that 
the three genera under consideration are retrograde descendants of Carboniferous 
Bellerophontiide and not remnants of types that flourished only in Cambrian and 
Lower Silurian times. Besides, this idea is entirely harmonious with laws that 
have been shown to operate in other branches of zodlogy, and according to which 
the earliest and latest representatives of a group of organisms may be more like 
each other than either is like intervening stages in the rise, acme and decline of the 
line of evolution to which they belong. 
Mogulia, in the absence of a slit-band, the shape of the outer lip, the form of the 
aperture, and even in the strength and course of the lines of growth on the dorsum, 
compares Closely only with Owenella, that most ancient of all the Bellerophontacea. 
Warthia, excepting that it has no spiral surface lines, nor those grano-lineate exten- 
sions of the inner lip, is precisely like that important group of Lower Silurian 
shells which we have called Protowarthia. Euphemus, again, in its broad and ridge- 
bordered slit-band, in the shape of the aperture, indeed in the form and characters 
of the whole shell, recalls the Lower Silurian genus Tetranota probably more than 
either Owenella and Protowarthia. But in the spiral columellar folds which spread 
over the umbilical regions and a large part of the dorsum of the last volution, we 
