alized
crown of still longer ones at the oral end; they arise outside of the
skeletal elements and do not pass between them, as in _Coleps_.

KEY TO MARINE GENERA OF TRACHELINIDAE.

Diagnostic characters: Body bilateral, or asymmetrical by local
prolongations; usually compressed or flattened laterally, the left
side more convex than the right. The essential feature is the
position and character of the mouth. This is either a long slit
extending from the anterior end well down the ventral surface, or the
posterior part only of a ventral furrow remains open as a round or
elongate mouth some distance from the anterior end. The entire mouth
region of the body is usually drawn out into an elongate tapering
proboscis which is generally curved dorsally at the extremity.
An oesophagus is short or absent altogether; when present it is
supported by a stiff buccal armature. Cilia are uniform about entire
body or limited to the flat right side. Food is swallowed.

1. a. Proboscis easily distinguished 2
from the main body

b. Proboscis not marked off from Genus *_Loxophyllum_
main body; body flat;
both surfaces striated

2. a. Mouth runs the entire length Genus _Amphileptus_
of proboscis; entire body
uniformly ciliated

b. Mouth runs the entire length Genus *_Lionotus_
of proboscis; body flat; right
side only is ciliated

c. Proboscis much drawn out, Genus _Dileptus_
flexible; mouth at its base

* Presence at Woods Hole indicated by asterisk.

Genus LOXOPHYLLUM Dujardin '41.

(Duj. '41; Wrzesniowski '69; Quennerstedt '65; '67; Cohn '66; Entz
'84; Gourret & Roeser '88; Buetschli '88; Shevyakov '96.)

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,