[Illustration: Fig. 62.--_Cothurnia crystallina_.] Cothurnia imberbis Ehrenberg, var. curvula Entz. Fig. 63. Synonyms: _C. imberbis_ Kent et al.; _C. curvula_ Entz; _C. socialis_ Gruber? The lorica is swollen posteriorly, narrowest at the oral margin, bent on its axis and is supported on a short stalk. It is perfectly smooth and without annulations. The animal itself has no definite stalk. When fully expanded the animal emerges but slightly from the margin of the cup. Fresh and salt water. On red algæ. Dimensions of Woods Hole form: Cup 50 to 55µ long; greatest diameter 22µ; length of stalk 4 to 5µ. [Illustration: Fig. 63.--_Cothurnia imberbis_.] Cothurnia nodosa Claparède & Lachmann. Fig.64. A. Smooth cup.--_Cothurnia maritima_ Ehr., Eichwald, Stein, Kent. B. Cross-ringed cup.--_C. pupa_ Eichwald, Stein, Cohn; _C. nodosa_ Cl & L.; _V. crystallina_ Entz '78; _C. pontica_ Meresch., Kent; _C. cohnii_ and _pupa_ Kent; _C. longipes_ Kellicott '94. The cup is elongated, swollen centrally, tapering at oral end and conical at base or rounded. Oral opening either circular or elliptical. Cross rings may or may not be present, and the cup is either smooth or annulate. Length of cup 70µ to 80µ. The stalk which supports the cup is extremely variable in length. The animal is borne upon a stalk of variable length within the cup. Entz states that the many variations which this species exhibits run into each other so gradually that he does not believe it wise to separate them. The Woods Hole forms which I found on algæ of various kinds were nearly of a size, and did not vary much from the one figured. Kellicott '94 described a _Cothurnia_ from Woods Hole under the name of _C. longipes_, which I believe is only a long-stemmed variety of _C. nodosa_. My form has the following dimensions: Cup 75µ; cup stalk 38µ; animal stalk 14µ. [Illustration: Fig. 64.--_Cothurnia nodosa_.] KEY TO FAMILIES OF SUCTORIA. a. Unattached forms; ventral cilia _Hypocomidæ_ present; one suctorial tentacle b. Attached forms; thecate and _Urnulidæ_ athecate tentacles simple, one or two in number c. Thecate; posterior end of cup _Metacinetidæ_ drawn out into stalk; walls perforated for exit of tentacles d. Stalked or unstalked; globular; _Podophryidæ_ tentacles of different kinds, some (2 genera *_Ephelota_, knobbed, others pointed *_Podophrya_) e. Naked or thecate; stalked or not; _Acinetidæ_ tentacles numerous, usually knobbed and all alike f. Naked; athecate; tentacles _Dendrosomidæ_ numerous, all alike, knobbed and grouped in tufts. They may be simple or branched. g. Sessile forms resting on basal _Dendrocometidæ_ surface or on a portion raised like a stalk; tentacles many; short and knobbed; distributed on apical surface or localized on branched arms