iv PHYLUM CCELENTERATA 185 



organisms, are able, in the case of the larger species, to capture 

 and digest Crustaceans and Fishes of considerable size. In many 

 cases small fishes accompany the larger forms and take shelter 

 under the umbrella. 



Considering the extremely perishable nature of these organisms, 

 and the fact that many of them contain not more than 1 per cent. 

 of solid matter, it is not to be expected that many of them should 

 have left traces of their existence in the fossil state. Nevertheless, 

 in the finely grained limestone of Solenhofen, in Bavaria, belong- 

 ing to the Upper Jurassic period, remarkably perfect impressions 

 of Jelly-fishes have been found, some of them readily recognisable 

 as Discomedusse. 



CLASS III. ACTINOZOA. 



1. EXAMPLE OF THE CLASS. A SEA- ANEMONE 



(Tealia crassicornis). 



Sea-anemones are amongst the most abundant and best known 

 of shore-animals. They are found attached to rocks, sea-weeds, 

 shells, &c., either in rock-pools or on rocks left high and dry by the 

 ebbing tide. Usually their flower-like form and brilliant colour 

 make them very conspicuous objects, but many kinds cover them- 

 selves more or less completely with sand and stones, and contract 

 so much when left uncovered by water, that they appear like soft 

 shapeless lumps stuck over with stones, and thus easily escape 

 observation. Any of the numerous species will serve as an 

 example of the group : the form specially selected is the " Dahlia 

 Wartlet" (Tealia crassicornis), one of the commonest British 

 species. 



External characters.- -Tealia (Fig. 137, A) has the form of a 

 cylinder, the diameter of which slightly exceeds its height. It is 

 often as much as 3 inches (8 cm.) across, is of a green or red colour, 

 and habitually covers itself with bits of shell, small stones, &c. It 

 is attached to a rock or other support by a broad sole-like base, 

 sharply separated from an upright cylindrical wall or column, the 

 surface of which is beset with rows of adhesive warts or tubercles : 

 at its upper or distal end the column passes into a horizontal plate, 

 the disc or peristome. In the middle of the disc, and slightly 

 elevated above its surface, is an elongated slit-like aperture, the 

 mouth (mth.\ from which streaks of colour radiate outwards. 

 Springing from the disc and encircling the mouth are numerous 

 short conical tentacles (t.\ which appear at first sight to be 

 arranged irregularly, but are actually disposed in five circlets, of 

 which the innermost contains five, the next five, the third ten, 



