In the family Cynthiidæ the test is usually leathery, the branchial and atrial apertures four-lobed, and the branchial sac folded into longitudinal pleats.
The genera Boltenia and Culeolus include species in which the body is attached to a peduncle.
The large exhibited specimen of Boltenia pachydermatina is 28 inches in length, the head being 4 and the stalk 24 inches long. The two four-lobed apertures are along one edge, the branchial being the lower; the body is marked with long deep furrows, and the stalk with transverse wrinkles. Culeolus perlucidus, from 1600 fathoms in the Southern Ocean, is in the form of a small pear-shaped head on a slender stalk, the total length being 4½ inches. The branchial orifice forms a transverse slit with raised lips near the stalk, the slit-like atrial orifice being near the rounded end of the body. Culeolus moseleyi, another slender-stalked form, was obtained from 2425 fathoms in the Central Pacific.
Fig. 11.
A. Styelopsis grossularia on shell. B. Tadpoles of same, × 9. a, branchial; b, atrial orifice. (B, after Sir J. Dalyell.)
The little Cynthiid Styelopsis grossularia (Fig. 11), popularly known as the “Currant Squirter,” occurs in the form of bright red hemispherical blobs on stones and shells; when undisturbed, the branchial and atrial orifices expand and project upwards. The eggs are brilliant red in colour. Sir John Dalyell was the first to discover the tadpole form, which is about ⅒ inch long (Fig. 11, B), and to observe the tadpoles become fixed and develop into fixed Ascidians. He calls the active little swimming larvæ “Spinulæ,” from their resemblance to small pins.
The family Ascidiidæ includes forms with a gelatinous or cartilaginous test; the branchial and atrial orifices usually have 8 and 6 lobes respectively; the branchial sac is without folds.
Ascidia mentula, described above, belongs to this family.
Chelyosoma is characterised by the test forming tortoise-like horny plates on the upper surface. The exhibited specimen of C. macleayanum (Fig. 12) comes from Greenland; the upper hemispherical part of the test is divided into 8 plates; the branchial and atrial orifices are situated in the joints between the plates.
