12 LAWSON, ON LIMAX MAXIMUS. 
of lime, which give that portion lining the visceral chamber 
a pure, white, lustrous aspect. I have not entered into the 
shell question in these pages, because the shell in its mature 
form is more or less structureless, and its homologies can only 
be arrived at by an appeal to development, the study of 
which in this animal I have not devoted sufficient atten- 
tion to.* 
Muscular System.—The muscles in this animal are not 
numerous, as, indeed, they are not in any mollusk, and may 
be conveniently grouped under two heads—those blended 
with the integument, and those distinct. The former I have 
already described. The isolated muscles are very few in 
number, and embrace those of the tentacula, and the retractors 
of the head. In both cases they are flattened bands, of a 
glistening, semi-transparent appearance, and are made up of 
long, fusiform endoplasts, with dark nuclei, and surrounded by 
a clear periplast. The retractor of the head is along, tough, flat 
band, which arises from the integument of the right side, 
about the middle of the antero-posterior plane, and, passing 
beneath the viscera reaches the nervous collar of the gullet ; 
here it comes through the circlet of nerves and beneath the 
cesophagus, and on approaching the head bifurcates, the 
two filaments thus produced being inserted into the musculo- 
fibrous tissue of the head, with which they become continuous. 
The tentacular are much more complex in mode of arrange- 
ment, and are three in number for each side of the body. 
These three are united in such a manner as to give rise to a 
more or less perfect equilateral triangle, whose base lies in 
the longitudinal plane, with the apex poimting laterally and a 
little upwards ; the posterior extremity of the base is con- 
tinuous with the dense skin of the foot, to which it is attached, 
and the anterior side is prolonged and blended with the tissue 
of the foot in the median line and just below the mouth. 
From the apex of the triangle springs the superior tentacle, 
and from the muscle constituting the base arises the inferior 
one; hence, if the basal cord contracts, the superior tentacle 
will be drawn in; if the posterior side of the triangle is 
shortened, the inferior tentacle will be brought in; and should 
the anterior band be stimulated, it will tend more or less by 
its contraction, to place both tentacula in a position to allow 
of eversion by the usual means. A glance at the semi- 
schematic figure on Pl. II will suffice to make these remarks 
intelligible. 
* For an admirable memoir on this subject, consult “ Beitrige zur Ent- 
wickelungsgeschichte der Land-Gasteropoden,” by Carl Gegenbaur, in 
Siebold und Kolliker’s ‘ Zeitschrift,’ &e., for 1852. 
