b. Peristomial area a broad Family _Bursaridæ_
triangular area ending in mouth

c. Peristomial depression short; Family _Stentoridæ_
limited to the anterior end; its
plane at right angles to the
long axis of body; surface of
peristome striated and ciliated;
no undulating membranes

2. _Oligotrichina_.

a. Peristome without cilia; cilia Family _Halteriidæ_
limited to one or more girdles
about body

One marine genus *_Strombidium_

b. Thecate forms; the body is Family _Tintinnidæ_
attached by a stalk to the cup;
within the adoral zone is a ring
of cilia.

c. The peristomial depression is Family _Ophryoscolecidæ_
deep and funnel-like; cuticle
thick, with posterior spine-like
processes.

* Presence at Woods Hole indicated by asterisk.