OHARACTERISTIO DEEP-SEA TYPES. — SPONGES. 175 
beautiful specimens collected off Frederichsteed in 180 to 208 
fathoms, in thick globigerina ooze. A fine Holtenia Pourta- 
lesii (Figs. 531, 531 a, 531 b, 531 c) was collected by Pourtalès 
off Sand Key, in depths varying from 184 to 324 fathoms. 
The group of Lithistidie, as defined by Zittel, includes 
sponges, formerly united with the Hexactinellid:e, characterized 
N fa S | 
UNITS 
CALO TSO » 
^ 
Fig. 532, — Vetulina stalactites. jreatly magnified. — (Sehmidt.) 
by their connected calcareous spicules (Fig. 532), not built upon 
the three-axis type, but forming an apparently irregular maze. 
The majority of the specimens of Vetulina stalactites (Fig. 
533) are thick, undulating sheets, closely perforated with irreg- 
= 
R 
, 583. — Vetulina stalactites. 4. 
ularly placed pores. The arrangement of the calcareous skele- 
ton recalls to a certain extent that of the Hexactinellidæ. The 
