176 THREE CRUISES OF THE “BLAKE.” 
genus Vetulina was previously known only from the Jura; it 
was quite commonly dredged off Barbados in 100 fathoms. An 
allied sponge, from 292 fathoms off Morro Light, Havana, is 
the little pear-shaped Collinella inscripta (Fig. 534), of which 
the fossil precursor may have been Trachysycon. Resembling 
Sulcastrella clausa (Fig. 535), dredged off Sand Key in 129 
Fig. 534. — Collinella inscripta. 3. Fig. 535. — Suleastrella clausa. 4. 
fathoms, are a number of cretaceous sponges to which Zittel 
has given the name of Astrobolia. 
Cup-shaped sponges having bunches of spicules scattered over 
the surface, like Setidium (Fig. 536), are unusual among the 
Fig. 536. — Setidium obtectum. 2. 
Lithistide. An interesting lithistid is a small form, Tremauli- 
dium, geminum (Fig. 537), in which the pores are replaced by 
an inward tubular extension of the cuticle. 
Fig. 537. — Tremaulidium geminum. 4. 
