GENUS XEROPHILA. 113 
The light thrown upon the relationship and affinity of the various forms 
by the more precise and intimate investigations of the present day, leads us 
to doubt the truth of the allocation of many species formerly associated 
together as simple variants of a common specific type, and though conti- 
nental authors have discriminated between many forms of this and other 
groups ina much more analytical way than is usual in this country, this 
action was usually based chiefly or entirely upon shell characters; yet 
some of their proposed species have already been justified by a demon- 
stration of certain differences in their organization as compared with that 
of the species to which they have hitherto been referred. 
The various species of the group have been carefully studied by the 
Marquis di Monterosato, who has devised sectional names, variant of 
Verophila, for the reception of the various types ; thus he proposes .Ve70- 
laxa for X. ttala and .Y. pamplonensis ; Nerocincta for .V. neglecta ; 
Neroleuta for \. obvia ; Nerogyra for \. bathyomphala and X. spade : 
Nerofriga for V. nubigena, ete. ; while Westerlund established a group 
as Pseudoxerophila for \. instabilis Zieg|. and allied forms, characterized 
by the shells bearing fine spiral strize and rows of punctiform impressions. 
The REPRODUCTIVE ORGANS show a well-developed penis and epiphallus, 
which is furnished with a strong retractor, and terminated by a short 
subulate flagellum ; the stylophore may be incompletely bifid, reduced to 
a simple sac, or in extreme forms entirely lost or modified into an organ 
of analogous function; the gypsobelum or dart may be paired, single, or 
even wanting; the mucus glands are 8-25 in number ; and the male element 
is transferred by means of a long, slender, and serrate spermatophore. 
The MANDIBLE is wide and arcuate with many more or less prominent, 
flattened, diverging, transverse ribs, which denticulate the cutting margin. 
The RADULA is of the usual type, with symmetrically trifid median teeth, 
asymmetrically bifid laterals, and trifid or quadrifid marginals. 
The species of this genus are extremely variable and especially numerous 
in the Mediterranean region, where the species are inextricably interwoven. 
‘he genus is, however, quite rare in North Central Europe, where the chief 
evolutionary area is assumed to have been located. 
According to Prof. Pilsbry, though the genus has been recorded from the 
Lower Miocene strata, there are few undoubted representatives before the 
advent of Pleistocene time. 
Fic. 167.—Stonehenge, Salisbury Plain, in 1898, where Verofhila ftala, NX. virgata, etc., 
are abundant (photo. by the late Mr. J. Madison, Birmingham). 
14/7/21 H 
