Synonyms. _Amphileptus fasciola_ Ehr. '38; Dujardin '41; Lachmann '56; Cohn '66, Diesing '65. _Loxophyllum fasciola_ Claparède & Lachmann '58; Balbiani '61. _Loxophyllum duplostriatum_ Maupas '83. Shevyakov '96. Body frequently brown or brilliant yellow in color, somewhat sigmoid in form with tapering anterior end, the extremity of which is turned dorsally. The proboscis is about half the entire length and is not sharply marked from the rest of the body but tapers gradually, its base being equal to the diameter of the body at its middle point. The body is slightly contractile and the posterior end is carried to a rounded point, but not into a distinct tail. Unlike the fresh-water variety, this one has no hyaline margin nor hyaline caudal region, and the contractile vacuole is double or multiple on the dorsal side near the posterior end. Cilia are present only on the under (right) side, with, however, a row of large cilia marking the course of the elongate mouth, upon its left side. The right side is striated, the left arched and without markings. The endoplasm is finely granular with, however, larger food particles in the process of digestion, while specimens are occasionally seen with the natural form completely lost through distortion caused by over-large captures (Cf. also Wrzesniowski '70, p. XXIII, fig. 32). Movement continuous, slow, and gliding; very little tendency to jerking movements. Macronucleus double, both parts spherical, and placed in about the center of the larger part of the body; closely approximated but not, as Schewiakoff described, connected. In conjugation, a large form unites with a smaller one, the mouth parts being connected. Details of conjugation and macronuclei not made out. Length 200µ to 600µ. [Illustration: Fig. 33.--_Lionotus fasciola_.] KEY TO MARINE GENERA OF CHLAMYDODONTIDÆ. Diagnostic characters: Form usually ellipsoid, never very elongate. Transverse section of body circular or elliptical. The mouth is usually some distance from the anterior end and may be in the posterior part. Sometimes it is in the center of the ventral surface, again on the right side. The oesophagus invariably has a well-developed buccal armature, or a smooth peculiarly built oesophageal tube. Food particles of large size. 1. Body cylindrical. Cilia about Genus *_Nassula_ entire body Body flat 2 2. a. Without a caudal process 3 b. With a caudal process 5 3. a. Anterior end angular 4 on left side b. Anterior end rounded Genus _Chlamydodon_ 4. a. Dorsal striæ and cilia present, Genus _Orthodon_ ventral cilia longer b. Dorsal striæ and cilia absent; Genus *_Chilodon_ posterior end not pointed c. Dorsal striæ and cilia absent; Genus _Scaphidiodon_ posterior end pointed