246 TOWARDS THE HUMAN FORM 



polyps cease building in waters whose temperature falls 

 below 25" C. So abundant are their remains that they 

 constitute huge calcareous formations, providing the name 

 for the Coralline division of the Jurassic. 



The Oolitic limestone, which plays so large a part in the strata 

 of this epoch, is simply a precipitate of the calcareous granular 

 dust, formed from broken-off pieces of polyparies after 

 they have been battered about in the waves, which collects 

 round debris of one sort or another. In its fossilized form 

 it has given the name to one of the two main subdivisions of 

 the Jurassic. 



In the seas encircled by these coral-builders a whole world 

 of new invertebrates found a home. Elegant Radiolaria 1 

 floated in the water, and the rocks blossomed with every sort 

 of siliceous and calcareous Sponge, 2 with Polyps, and with 

 Crinoids so closely resembling plants that they are called 

 Sea-Lilies when they attach themselves by a stalk to the sea- 

 bottom and look like living flowers, and marine Palms when 

 they spread out at the summit of their fifty-foot stems great 

 plumes that looked exactly like the leaves of date-palms, as 

 the Pentacrinoids do that still exist as green meadows in the 

 waters off Rochefort. 



It was at this time that some of these Sea-Palms detached 

 themselves from their stems, and gave rise to new free forms 

 like our modern five-armed Eudiocrinus, which lives in the 

 depths of the Pacific and the Atlantic ; to Comatida, which 

 has ten tentacles like rose-coloured feathers and swims in 

 a leisurely fashion by undulating them alternately ; and to 

 Actinometra, an inhabitant of the warm seas, whose ten 

 primitive arms have an indefinite number of ramified branches. 

 Over these reefs, gay and glowing as those of whose incompar- 

 able beauty Saville Kent has written, countless Molluscs 

 dragged shells which displayed an infinite variety of new 

 forms. For, in addition to the surbased forms and those 

 with rounded openings there were Scalaria and Turitellidae with 

 long shells and corkscrew turns, Natica? and others with rounded 

 and polished shells, large Strombidae with long scooped-out 

 orifices, many forms of carnivorous Gasteropods with shells 

 either notched or drawn out into a tube, Cerithium, Fusella, etc. 



1 Spumellaria and Nassularia. 



2 Hexactinellidae, Tetractinellidae, Lithistidese, Monactinellidae, Phare- 

 tronids and other calcareous Sponges. 



