110 



COELENTERATA CNIDARIA 



CLASS II 



provided with pseudosepta and columellae, and communicate with the zooid 

 tubes and vermiform canals. Recent, and occurring sparsely in the Tertiary. 



Order 3. TUBULARIAE. Airman. 



Polyp stocks which are either naked or covered with chitinous outer layer (periderm). 



Both the polypoid nutritive zooids, and also the medusoid reproductive animals are 



without cup-shaped hydrothecae surrounding the polyp head. A chitinous or calcareous 



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 

 pillars). The surface is 

 covered with projecting 

 hollow spines and tuber- 

 cles, and is also traversed 

 by shallow, branching 

 grooves (astrorhizae). In- 

 terlaminar spaces com- 

 municating with the sur- 

 face by means of rounded 

 tubes. Tertiary and 

 Recent. 



Ellipsactinia, Steinm. 

 Hydrophyton irregu- 

 larly ellipsoidal, com- 



FIG. 194. 



A, Hydractinia echiwato, Flem. Recent ; North Sea. Portion of parasitic 

 colony, greatly enlarged ; hy, Polyps (hydranths) ; go, Generative buds 

 (gonophores) ; hph, Hydrophyton adherent to shell of Buccinium undatum, 

 and showing reticulated structure in vertical section. B, Hydractinia 

 calcarea, Cart. Vertical section of hydrophyton, greatly enlarged (after 

 Carter) ; a, Primary basal lamella ; b, Interlaminar space ; c, Second 

 lamella ; d, Radial pillars between the lamellae ; e, f, Tubercles and spines posed of thick, COnCCn- 

 prqjecting on upper surface. C, Hydractinia pliocaena, Allm. Pliocene; ~_ . ,. , -. 

 Asti, Italy. Hydrophyton encrusting on Nassa shell (natural size). triC, Slightly Separated, 

 D, Portion of magnified surface of the latter, showing branching grooves a 1 Q T .Q rtlia Inrnolla^ 



and wart-iike tubercles. calcareous lamellae, 



w T hich 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, Steinm. 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 

 calcareous 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 



