MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 97 
H radiatula electrina Gould. 
Helix electrina Gould, Invert. Mass., 1841, p. 183, f. 111. 
Hyalina viridula Binney, L. & F. Shellsof N. Amer., 1869, p. 34, f. 41-43. 
Vitrea hammonis Pilsbry, Nautilus, 1898, p. 129. 
Vitrea radiatu/a Dall, Land and Freshw. Moll. of Alaska, Harriman Exped., 1905, p. 38. 
HIS interesting Nearctic 
race of Hyulinia radiatula 
[ have very great pleasure in 
associating with Mr. G. H. Clapp 
of Pittsburgh, U.S.A., an ardent 
and successtul scientist, who is 
in the forefront of American 
conchology, and very intimately 
identified with the modern ad- 
vancement of the study of the 
mollusea of the United States, 
and is doing so much excellent 
work to assist in the elucidation 
of the variation and also in the 
definition of more precise specific 
limits of the present and other 
species. 
Original Description. —‘‘ Hyalina 
electrina. Shell small, depressed, 
pellucid, fragile, amber-coloured ; 
whorls 4, conspicuously 
wrinkled by the lines of 
growth;aperturerounded; 
lip simple; umbilicated.” 
—GOULD’S Invert. Mass., 
2nd ed., 1870, p. 397, f. 656. 
Although Gould’s original deseription of Helix electrina includes only the amber- 
coloured form, and Binney and Bland in their description of the same species under 
the name of H. viridula Menke are equally stringent in their limitations, yet this 
— 
eo 
Fic. 139.—Outlines of the upper, basal, and frontal aspects of //. radiatula electrina Gould, from 
Cambridge, Mass., X 9. (After camera lucida drawings by Mr. G. H. Clapp). 
variety or race also presents the horny and the erystalline forms, as in the typical 
radiatula, but the shell has been hitherto indiscriminately recorded in American 
literature under the various names of electrina, hammonis, radiatula and viridula, 
without any serious attempt being made to formulate or indicate the differences 
that exist in the striation and colour of the shell. 
\ ( © » \ \ “le i 5 | | { O ) 
ee ae ee Cas 
Ais see cov. : = ow Pa 
Fic. 140.—Outlines of the upper, frontal, and basal aspects of H. radiatula electrina var. 
circumstriata, from Wetumpka, Alabama, U.S. x 5. (After camera lucida drawings by Mr. G. H. 
Clapp). 
12/8/08 ‘ 
