MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 4635 
Hyalinia helvetica (Blum). 
Synonymy.——This species was believed by the late M. Bourguignat 
and many continental conchologists to be the true //. alliaria of Miller, 
M. Bourguignat basing his belief on receiving specimens from Lovell 
Reeve and other English conchologists under that name. 
Diagnosis.—The sinuate upper margin of the aperture shown in the 
figures of this species (see pl. 6) though an usual feature of the shell, 
cannot be absolutely relied upon as a specific character. 
The dissections by the Rev. E. W. W. Bowell of a continental specimen 
of Hyalinia helvetica and of what he terms Vitrea royersi are given for 
comparison with each other and with 
those given on p.48 which represents 
the form presented by a very large 
number of dissections and drawings 
of British specimens. 
According to Mr. Bowell, the 
proximal parts of the genitalia in 
the continental //. helvetica show 
an extremely short vas deferens, 
commencing two-thirds of the way 
down the penis-sheath, and a shoe- 
shaped spermatheca with a short, 
stout and twisted duet, while he 
states that rogersi has a soft and 
flexible stem, which he figures as of Fic. 538.—-Dissection of the proximal part of 
a very abnormal length, while the the Reproductive system of //. he/vetica Blum, 
flexures of the vas deferens shown °™ Solothurn, enlarged (after Bowell). 
: 3 : 7 Fic. 539.—Dissection of the proximal part of 
in the figure are, he observes, found the Reproductive system of //. vegersi B.B.W., 
to exist almost uniformly. from Westerham, enlarged (after Bowell). 
The radula of //. helvetica Blum, from Solothurn, is in the opinion of 
Mr. Bowell, a very characteristic organ, and by it, he says, the species 
may be distinguished from other Vtrew, the central tooth being small, 
its basal plate remarkably quadrate, and the central cusp long. There 
are only two well-developed laterals, and these are also remarkable for 
the squared character of their basal plates ; their mesocones and endo- 
cones are of a compactly rounded shape, and the ectocones are closer than 
usual to the mesocones on account of the abbreviated shape of the teeth. 
There are 13 to 16 closely-set marginals, with very curved basal plates, 
and cusps of average length, which only slightly overlap the next row, 
the first marginals may be regarded as either transitional, or as a. first 
marginal, being furnished with a slight endoconic prominence, 
Fic. 538. Fic. 539. 
The radula of vogers/, from Westerham, is stated by Mr. Bowell to be 
very non-significantly variable, and due mainly to looseness of build, the 
central tooth being frequently asymmetrical, with a considerable variation 
in the length of the mesocone, which is rounded or ovate in shape, and 
may bear an additional ectocone on one side. ‘The exact shape of the 
admedians is also said to be very variable, and their mesocones are more 
slender, while the ectocones show a tendency to disappear, or are so 
reduced as to suggest a serration ; and one never sees the neat and dis- 
tinct quadration of the basal plate, said to be so strongly marked in 
