192 POLYZOA 



size, since mesopores, acanthopores, avicularia, and vibra- 

 cula are generally absent ; the apertures are round and 

 terminal, not constricted and not provided with an oper- 

 culum. There may be a brood-pouch, termed a gonoecium 

 or gonocyst, formed of one or of several specially modified 

 individuals, but ocecia, such as are characteristic of the 

 Cheilostomata, are always absent. The Cyclostomata 

 range from the Ordovician to the present day. 



Stornatopora. Zoarium encrusting, of branching rows of 

 zocecia in single file. Ordovician to present day ; common in 

 Jurassic and Cretaceous. Ex. S. granulata, Cretaceous. 



Berenicea. Zoarium a thin, flat, encrusting sheet— discoid, 

 fan-shaped, or irregular. Zocecia simple, tubular, arranged in irregu- 

 larly alternating lines. Ordovician to present day — common in the 

 Jurassic and Cretaceous. Ex. B. diluvia?ia, Lias to Oxfordian. 



Idmonea. Zoarium encrusting or erect. Zocecia arranged in 

 alternating transverse rows on one face only of the zoarium. Jurassic 

 to present day. Ex. I. hagenowi, Lower Greensand. 



Entalophora. Zoarium of erect cylindrical branches, with 

 the zocecia opening on all sides of the branch and arranged irregu- 

 larly or quincuncially. Jurassic to present day. Ex. E. virgula, 

 Cretaceous. 



Theonoa { = Fascicular ia). Zoarium large, generally massive 

 and globose. Zocecia in the form of long tubes, with horizontal 

 tabulae, in contact laterally, and forming bundles which are either 

 distinct and radiate from the base to the periphery, or fuse into 

 laminae which intersect. Jurassic to Pliocene. Ex. T. aurantium, 

 Coralline Crag. 



SUB-ORDER II. TREPOSTOMATA 



The zocecia are calcareous, tubular, with transverse 



partitions, and of two sizes, the smaller apertures being 



known as mesopores and acanthopores ; avicularia and 



vibracula are absent. The apertures of the zocecia are 



