108 GASTEROPODA OF THE INFERIOR OOLITE. 
with a stout diverging pair of spines, or didactyl wing. Other indications are 
wanting. 
Relations and Distribution.—This species seems to be the descendant of the 
short variety of Sp. didactyla. A single specimen was found in the Sauzei-bed, 
or marl with green grains at Oborne. 
Genus—Ataria, Morris and Lycett, June, 1851. 
* Shell fusiform, turrited ; anterior canal straight or curved ; lip dilated, digitate 
or palmate, formed by the prolongation of the last whorl; no posterior canal ; no 
sinus properly so-called on the anterior margin of the lip; columellar margin not 
callous.” —FiscHER. 
The above diagnosis is substantially that of Piette (‘ Cont. de la Pal. Franc.,’ 
p- 16), who adopted Morris and Lycett’s genus with modification. Piette further 
alludes to the nakedness of the first whorls, which are smooth and convex, and 
also to the power of developing varices, spurs, and protuberances at various periods 
of increase, evident traces of rudimentary wings, which appeared usually on the 
side opposite the actual (definitive) wing. 
This very important genus has been variously subdivided into sections, to say 
nothing of sub-genera, such as Spinigera previously described. On the other 
hand, as already observed, there are not wanting those who fail to see any generic 
difference between Alaria and Aporrhais (Chenopus). Into these questions I do 
not feel disposed fully to enter, beg on the whole satisfied that the genus Alaria 
may fairly be taken to cover the remainder of the wing-shells of the Inferior 
Oolite, with possibly one or two exceptions. It would not be difficult for a casuist 
to prove, almost to demonstration, that the family of the Aporrhaidz consists of 
httle more than one genus. Thus Cossmann makes Malaptera (in part the old 
Jurassic Pterocera) co-generic with Aporrhais, which Gardner says does not differ 
from Alaria, of which Spinigera, according to Fischer, is merely a sub-genus. As 
was urged in the Introduction to this memoir, since the practical acceptance of 
the doctrine of evolution we no longer worship the fetish implied in such terms as 
“species,” ‘‘genus,” ‘family,’ &c. If no lawyer is able to draft an Act of 
Parliament through which some other lawyer cannot drive a coach-and-four, how 
much more applicable is this principle to the diagnosis of shells. 
As far as the shell goes we need not, I think, have much difficulty in separating 
Alaria from Aporrhais in the majority of cases, since the wing in Alaria is barely 
or, at best, but scantily palmate, and does not envelope more of the spire than the 
anterior half of the penultimate. The monodactyl Alarie are widely different from 
