FOSSIL ACTINOZOA. IOI 



together by a true coenenchyma. The septa are usually incomplete, but 

 are never porous, and never bear synapticulse. The order is divided into 

 the following four families : 

 Family I. Staurid<z. 



Corallum simple or composite ; septa incomplete, united by lamellar 



dissepiments ; four large primary septa, forming a cross. 

 Family 2. Cyathaxonidce. 



Corallum simple; septa complete; no dissepiments or tabulae; with- 

 out four primary septa. 

 Family 3. Cyathophyllida. 



Corallum simple or composite ; septa incomplete ; tabulae generally 



present. 

 Family 4. Cystiphyllidfe. 



Corallum simple, composed chiefly of a vesicular mass with but 

 slight traces of septa. 



ORDER III. ALCYONARIA. The Alcyonarian Zoophytes 

 differ from the Zoantharia in the fact that the polypes have eight 

 pinnately fringed tentacles, the mesenteries also being some multiple 

 of four. The Alcyonaria thus differ from the Zoantharia, and 

 agree with the Rugosa in the numerical proportion of their soft 

 parts. The Alcyonaria, however, differ from the Rugosa in 

 never possessing a sclerodermic coral divided by septa. When 

 they have a sclerodermic corallum at all, it either consists 

 simply of scattered spicules (as in Alcyoniuni), or, if thecal, 

 consists of simple tubes which are not subdivided by vertical 

 partitions or septa (as in the Tubiporida). We have, however, 

 nothing to do with these forms, as they are unknown in a 

 fossil condition. The only members of the Alcyonaria which 

 have left any traces of their past existence, are those which 

 possess a " sclerobasic " coral, in the form of a simple or 

 branched internal axis, which may be calcareous or corneous, 

 or partly the one and partly the other. Such forms are well 

 represented at the present day by the Sea-pens (Pennatulid<z\ 

 the Sea-shrubs and Red Coral (Gorgonida), the Fan -corals 

 (Rhipidogorgia), and the like. They are, however, of very small 

 palaeontological importance. 



The genus Protovirgularia has been constituted for the 

 reception of an obscure Silurian fossil, from its. supposed 

 affinity to the living Sea-rods ( Virgularia). This problematical 

 organism, however, is almost certainly not one of the Alcyona- 

 ria, and may, perhaps, belong to the Hydrozoa. With this 

 exception, and the still more dubious examples of Gorgonidcs. 

 from the Silurian Rocks, no Alcyonarian Zoophyte has been 

 detected in deposits older than the Chalk. One of the Pen- 

 natulida (viz., Graphularid} has been found in the London 

 Clay (Lower Eocene) ; and the same formation has likewise 

 yielded two species of Gorgonidcz (Mopsea and Websterid). 



