110 COELENTERATA—CNIDARIA CLASS II 
provided with pseudosepta and columellae, and communicate with the zodid 
tubes and vermiform canals. Recent, and occurring sparsely in the Tertiary. 
Order 3. TUBULARIAE. Allman. 
Polyp stocks which are either naked or covered with chitinous outer layer (periderm). 
Both the polypoid nutritive zovids, and also the medusoid reproductive animals are 
without cup-shaped hydrothecae surrounding the polyp head. A chitinous or caleareous 
skeleton (hydrophyton) is frequently secreted at the base. 
Hydractinia, v. Bened. (Fig. 194). Hydrophyton in the form of encrusting, 
chitinous, rarely calcareous expansion, frequently investing gastropod shells. 
The crust consists of 
successive, slightly sepa- 
rated, horizontal laminae, 
which are supported by 
numerous vertical rods 
or columns (radial 
pulars). The surface is 
covered with projecting 
hollow spines and tuber- 
cles, and is also traversed 
by shallow, branching 
grooves (astrorhizae). In- 
vor fh\ ct BEN! |) Wiepeek terlaminar spaces com- 
2 i 7p: J Seesssaired municating with the sur- 
SAE ee oN igor ’y face by means of rounded 
me tubes. Tertiary and 
A, Hydractinia echinata, Flem. Recent; North Sea. Portion of parasitic Recent. Soi . 
colony, greatly enlarged; hy, Polyps (hydranths) ; 90, Generative buds Ellipsactinia, Steinm. 
and ahowiie retiolldted structure in vertical section. 2, Mydracinia.| EL) Ox ODhy tame sami 
aise Cari, enucal seston of brdvopiyten, graty cileeet Se: larly lliptaaaa 
lamella ; d, Radial pillars between the lamellae ; ¢, f, Tubercles and spines posed of thick, concen- 
projecting on upper surface. C, Hydractinia pliocaena, Allm. Pliocene ; 5 A 
Asti, Italy. Hydrophyton encrusting on Nassa shell (natural size). tric, slightly separated, 
Pe en Ot eee surface of the latter, showing branching grooves caleareous lamellae, 
which are united by 
sparsely distributed vertical columns. Lamellae are formed by the anastomosis 
of exceedingly delicate calcareous fibres, punctured by numerous fine radial 
tubes, and furnished on both sides with pits, tubercles, and branching furrows. 
Upper Jurassic (Tithonian) ; Alps, Carpathians, and Apennines. 
Sphaeractinia, Stenm. Like the preceding, but composed of thin, widely 
separated lamellae, which are supported by numerous radial pillars. Centre 
frequently occupied by a foreign body. Upper Jurassic (Tithonian). 
? Loftusia, Brady (Fig. 195). Ellipsoidal or fusiform bodies, composed of 
thin, concentric, or spirally rolled calcareous lamellae. Interlaminar spaces 
wide, intersected by numerous radial pillars, and often secondarily filled with 
caleareous mud. Eocene; Persia. 
Parkeria, Carp. Globular or walnut-shaped organisms with nodulated 
exterior, and composed of rather thick, concentric, calcareous lamellae. Inter- 
laminar spaces divided into chamberlets by stout radial pillars, which usually 
— = 
®A>20 
tam 
ATs 1 

Fic. 194. 
