Variety armatum (Cl. & Lach.) Fig. 32.

Under the name _Litosolenus armatus_, Stokes described a form from
brackish water near New York, which should unquestionably be referred
to the genus _Loxophyllum_, and I believe to Quennerstedt's species
_setigerum_. While the latter possesses only a few setæ, the former
has a number of them, and Stokes described his species as having a
variable number. For this reason I include the Woods Hole form under
the tentative name _armatum_, as a variety of Quennerstedt's _L.
setigerum_. The flat margins are distinctly striated longitudinally,
and faintly marked radially, on the dorsal surface. Longitudinal
elevated striæ also run the length of the dorsal hump and upon the
entire ventral surface. The ventral surface is alone ciliated. Upon
the edges of the flat border are sharp-pointed, colorless, spine-like
processes, situated at equal distances around the entire periphery
except at the anterior end. Each spine is thick at the base and
tapers to a full point which is curved upward--_i. e._, dorsally
(fig. 32, a, b). The entire body is plastic and contractile, turning
its leaf-like edge readily over objects upon which it creeps. The
cilia are fine and uniform, with a tendency to lengthen in the oral
region.

Length 100µ; greatest width assumed on contraction 85µ; when normal
about 50µ.


[Illustration: Fig. 32.--_Loxophyllum setigerum_, var. _armatum_. a,
b, c, ventral, dorsal, and lateral aspects.]