294 



NATURAL HISTORY. 



Fossil Hydrozoa have been discovered, some without doubt analogous to recent forms, and others 

 not so. Impressions of medusae have been found on the Solenhofen stone, and they were Rhizostomida?. 

 The Graptolites or Rhabdophora are fossils in the shape of long, narrow, toothed (at the side) bodies, single 

 or combined. They are found in the Lower Silurian, and die out before the end of the Upper Silurian 

 group of strata. Two principal forms exist : those with one row, and those with two rows of cellules ; 

 and in Rastrites the cellules are separate, and not overlapping as in the others. They may have a 

 central disc or prong-like process at the end, with a central solid rod. The cellules analogous to the 

 calycles of Sertularians probably contained structures resembling nematophores. 



The Hydrocorallinse of the Millepore division have no satisfactory fossil species ; but there is a 

 doubtful form in the Cretaceous rocks. Probably most of the family Eavositidse, usually called 

 Tabulate Corals, were hydroids, and many of the corals called Rugosa. 



A fossil, with a root-like expansion, hollow stem, and tentacles, surrounded originally by a 

 calcareous investment, is found on the face of the fronds of a Carboniferous Bryozoon, Fenestella 

 nodulosa. It has been named Palaeocoryne of the Hydroida.* 



Order. 

 CTENOPHOKA 



DISCOPHORA, or ACALEPHA: 



SlPHONOPHORA 



TRACHOMEDUSA . 

 HYDROIDA. 



GROUP ZOOPHYTA. 



CLASS HYDROZOA, OR HYDROMEDUS^E. 

 Sub-order. 

 ( Globata . 

 \ Lobata 

 y Cestidae . 

 ( Eurystoma 

 fMonostoina 

 . . -< Rhizostoma 



{ Calycozoaria 



Physophora 



Physalia . 



Calycophora 



Discoida . 



Trachomedusae 



Tubularia Gymnoblastea 



Campanularia Calyptoblastea 



HYDROCORALLIN.S 



Example. 



Pleurobrachia. 



Bolina. 



Cestum. 



Beroe. 



Aurelia. 



Rhizostoma. 



Lucemaria. 



Physophora. 



Physalia. 



Diphyes. 



Velella. 



^Egina. 

 /Hydra, 

 j Perigonimus. 

 j Eudcndrium. 

 1 Hydractinia. 

 | Syncoryne. 

 ^Tubularia. 

 ( Sertularella. 

 ) Plumularia. 

 1 Campanularia. 

 ( Eucope. 

 I Millepora. 

 < Stylaster. 

 ( Cryptohelia. 



CHAPTER II. 



THE ANTHOZOA. 



Zoantharia and Alcyonaria Characters THE ZOANTHARIA The White Stony Corals or Madreporaria Structure The 

 Coral Development The Reef - builders Coral Islands MADREPORARIA APOROSA Turbinolidae Oculinidae 

 Astraeidae Eusmilinae Euphylliaceae Stylinaceae Lithophylliacese Astraeaceae Cladocoracese Fungidse 

 MADREPORARIA PERFORATA Eupsamminae Poritidae Other Groups of the Madreporaria ANTIPATHARIA OR 

 SCLEROBASIC ZOANTHARIA AcTiNAHiA OR MALACODERMic ZOANTHARIA Characters Actinidae Minyadinae Acti- 

 niuae The Sea Anemones THE ALCYONARIA Characters Helioporidae Pennatulidae or Sea-Pens GORGONIDJE 

 Red Coral Formation Gorgoninae Characters Various Genera Alcyonida; Distinctive Features Organ-pipe 

 Coral Alcyoninse Dead Man's Fingers Classification of Anthozoa. 



THE CLASS ANTHOZOA. 



THE White Stony Corals, Sea Anemones, and Antipatharia form one order of this class, the 



Zoantharia ; and the Red Coral, the Tube Coral, the Isis, and the Alcyonians are a second order called 



Alcyonaria ; and all of these familiar and beautiful objects merit the name of flower-like animals, from 



* The principal works on the Hydrozoa, quoted in this article, are those of Allman (Ray Society), Hincks, and Claus. 



