The body is flat and somewhat leaf-shape, flexible, and elastic.  The anterior end is somewhat proboscis-like and flexible, but is not sharply demarcated as in Lionotus.  The central portion of the body is developed into a more or less arched dorsal mass, which usually contains the nuclei and contractile vacuoles.  As a result of this local thickening, the body is surrounded by a thin hyaline margin.  This, however, may be absent on the right side in some species.  The mouth reaches from the anterior extremity to a short distance from the end, and usually approaches the left edge.  An anus is present near the posterior end of the dorsal swelling.  Trichocysts are numerous on the ventral surface, and often on the dorsal surface, where they are inclosed in minute papilla-like swellings.  Cilia-distribution controverted.  Maupas and Buetschli hold that ventral surface alone is ciliated; others (Kent and Dujardin) that cilia are uniformly distributed.  The entire body, dorsal and ventral surfaces alike, are uniformly striated.  The contractile vacuole lies posteriorly, on the right side and in the dorsal swelling.  In the fresh-water form L. meleagris, it is connected with a long canal whose swellings are frequently taken for additional contractile vesicles (Buetschli); in the marine form described below the canal is not developed and a series of vacuoles takes its place; these are all contractile.  The macronucleus may be single, double, quadruple, band-formed, or rosette-formed.  Movement is steadily progressive and peculiarly gliding.  Fresh and salt water.

Loxophyllum setigerum Quenn. ’67.

Synonyms:  Litosolenus armatus Stokes ’93; Litosolenus verrucosa
Stokes ’93.

The body is flattened, irregular in outline, obtusely pointed anteriorly, the point being turned to the right; rounded posteriorly.  The left edge is nearly straight, the right considerably arched with a few setae on the posterior half.  Contractile vacuoles are numerous, dorsal in position and on the right side.  The macronueleus is beaded, the several spheres connected.

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 setae, 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 striae 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,