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. 



Fig. 535. Sulcastrella clausa. . 



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. f . 



Lithistida3. An interesting lithistid is a small form, Tremauli- 

 dium yeminum (Fig. 537), in which the pores are replaced by 

 an inward tubular extension of the cuticle. 



Fig. 537. Tremaulidium geminum. ^. 



