FOSSIL ACTINOZOA. 



their mouths appear to be sunk below the general surface of 

 the polypary, forming a row of rounded or quadrangular open- 

 ings on each side. Both Dip- 

 lograpsus and Climacograpsus 

 range in Britain and North 

 America from the Upper Cam- 

 brian to the summit of the 

 Lower Silurian series ; but in 

 Bohemia they rise into the 

 lower portion of the Upper 

 Silurian deposits. In the genus 

 Dicranograpsus the polypary is 

 at first diprionidian, but soon 

 splits into two monoprionidian 

 branches which carry the cel- 

 lules along their outer margins. 

 The genus is exclusively Lower 

 Silurian. Lastly, the beautiful 

 genus Phyllograpsus may be 

 regarded as composed of two 

 Diplograpsi placed at right 

 angles to one another. It is 

 exclusively confined to the 

 Skiddaw and Quebec Rocks.* 



* The Student, desirous of fuller 

 information on this subject, may con- 

 sult the author's ' Monograph of 

 the British Graptolitidae, ' Part I., 

 General Introduction ; where full de- 

 tails are given as to the morphology 

 and affinities of these singular fossils. 



Fig- 35- A, Diplograpsus pristis, 

 His., slightly enlarged, showing the 



_pines ; C, Another of the same, 

 larged, 



proximi , _., , 



(Original.) 



nes ; C, Another of the same, en- 

 ged, showing lateral spines, succeeded 

 )ximally by a small bulb, but showing 

 true radicle. (Original.) 



CHAPTER IX. 

 FOSSIL ACTINOZOA. 



OF the living groups of the Actinozoa (see Table, p. 73), the 

 Ctenophora and the Sea-anemones (Zoantharia malacodermata), 

 from their absence of hard parts, are unknown in a fossil con- 

 dition. The remaining groups viz., faz Zoantharia sderobasica, 

 Zoantharia sclerodermata, Alcyonana, an&Rugosa secrete a hard 

 skeleton, which is known by the general name of the " coral " 



