MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 51 
Famity LIMACID.X Gray. 
The family Limacidw as here understood 
embraces the genera Limav, A griolimax 
and Amalia, mm addition to other groups 
foreign to our shores, and although now 
restricted in extent is not even yet a 
thoroughly homogeneous family, but the 
parallel course of ‘shell degeneration and 
the marked convergence of the external 
form of the constituent genera renders 
their association convenient, at least 
until their true genetic relationships 
have been elucidated. 
The great advances made in late years 
in our knowledge of these neglected 
creatures is largely due to the brillant 
researches of Dr. Simroth, the eminent 
a — — German limacologist, who has for years 
A A Oye te. made the elucidation of this group an 
z especial study. 
Family Characteristics.— ExTerNAL.y, the features possessed in com- 
mon by the Limacidw are the elongate, subcylindrical Bopy ; a more or less 
noticeable DORSAL KEEL, most pronounced at the caudal end; an anterior 
mantle or SHIELD which covers the pulmonary chamber, the heart, the kid- 
ney, etc., with the RESPIRATORY APERTURE on the right side, behind the 
middle of the mantle margin ; SOLE longitudinally tripartite, mid-area loco- 
motory ; REPRODUCTORY ORIFICE behind the nght ommatophore. 
SHELL oblong or oval, white and slightly concave, with the nucleus at the 
posterior margin, but inclining towards the left side, from whence concentric 
hnes of gr owth extend, which demonstrate that the external shell of which it 
is the vestige was spirally coiled; the Dendrolimaces of South Africa show 
more clearly the stages between the shelled and the naked species. 
INTERNALLY, the NERVOUS SysTEM is chiefly aggregated around the 
pharynx’; an important caudo-dorsal nerve arises from the pallio-abdominal 
commissure, extends along the length of the body, and is in intimate con- 
nection with the pharyngeal retractor : ; MANDIBLE oxygnathous’; LINGUAL 
TEETH numerous, arranged in median, lateral and marginal series and quite 
typical of the group Dichoglossa*: : pharyngeal and tentacular RETRACTORS 
combined posteriorly and forming a common stem affixed to the dorsal 
integument behind the lung, and constituting with the testaceous forms 
the group Monorhiza.* 
The Limacide is one of the groups which retain in adult life the primi- 
tive shell or protoconch’ formed by the shell-gland of the embryo; and 
which also develop in the Gastrula® stage a well-marked caudal vesicle, 
whose rhythmical contractions assist the circulation of the be ly fluids prior 
to the developing heart becoming functional. 
The shell is the lapis limacum of the Romans, and enjoyed great re- 
nown amongst the various remedies,’ bezoars, and eaminlere® which ancient 
peoples held in high esteem either as specifics for the cure of various ail- 
ments or as charms protecting the wearer against accidents or disease. 
1 Monog. i.. p. 215, f. 424 2 Monog. i., p. 255, f. 511. 3 Monog. i., p. 271, f. 543. 
4 Monog. i., p. 343, f. 637. 5 Monog. i., p. 322. 6 Monog. i., p. 380, f. 717. 7 Monog. i., p. 427. 
8 Monog. i., p. 433. 
