LIFE IN THE MESOZOIC EPOCH 465 



MESOZOIC HEDGEHOG- SKINNED ANIMALS (ECHINODERMATA). 

 Sea- Lilies (Crinoidea) were far less dominant than during the 

 Palaeozoic epoch, and were represented by types of different kind, 

 some of them (e.g. Pentacrinus] being closely allied to forms now 

 living in the deep sea. Feather- Stars, belonging to the same 

 class, but distinguished by the fact that when adult they abandon 

 their stalks and take to a free life, first made their appearance 

 during this epoch. 



Ordinary Star- Fishes (Asteroidea) and Brittle- Stars (Ophiu- 

 roided) were of increasing importance, and very numerous Sea- 

 Urchins (Echinoidea) existed, many of them resembling recent 

 forms, and differing greatly from the primitive palaeozoic types. 



MESOZOIC LAMP-SHELLS (BRACHI- 

 OPODA). These lost their dominance 

 during this epoch, and the most im- 

 portant species belonged to genera 

 which are represented at the present 

 day (e.g. Terebratula and Rhync ho- 

 ne lid). 



MESOZOIC JOINTED- LIMBED ANI- 

 MALS (ARTHROPODA). The Trilobites 

 and Eurypterids of the Palaeozoic 



- . _ Fig. 1321. Shell of an Ammonite (reduced) 



epoch were entirely unrepresented, 



but undoubted Crustaceans (Crustacea) were common. These 

 included numerous species belonging to the highest order 

 (Decapodd), and more or less resembling the Lobsters, Prawns, 

 Shrimps, and Crabs of the present day. 



Among the air-breathing forms Insects (Insectd) were 

 gradually acquiring a dominant position. Of orders for the 

 first time represented may be mentioned Beetles (Coleopterd), 

 Flies (Dipterd), and Membrane -Wings (Hymenopterd). Ants 

 are the most ancient members of the last order, so far as the 

 evidence goes. 



MESOZOIC MOLLUSCS (MOLLUSCA). Head-Footed Molluscs 

 (Cephalopoda) took a leading place in the marine fauna. Two 

 important types, i.e. Ammonites and Belemnites, were practically 

 limited to the epoch. The former (fig. 1321) possessed spiral 

 chambered shells, with the turns in one plane, and the edges of 

 the partitions between the successive chambers elaborately folded. 

 Towards the end of the epoch, however, we find more or less 



