206 ECHINODERMS OF THE BRITISH ISLES 



Ophiopluteus, with simple body skeleton (Fig. 88, 5), each trans- 

 verse rod with a forwardly directed process. Postero- lateral 

 arms of medium length. Breeding season June- July. 



In British seas this species is common all round the coasts, 

 though scarcer along the south coast ; also recorded from the 

 Rockall Bank. It seems to be rare below ca. 300 metres, but 

 has been found at a depth of ca. 1000 m. in the Faroe Channel 

 (" Porcupine "). It is widely distributed in the Arctic seas, 

 circumpolar, and occurs along the Scandinavian coasts down to 

 the Sound and the Belts ; its southern limit in European seas is 

 the British south coast. On the American side of the Atlantic 

 it goes as far south as Cape Cod. Also in the Northern Pacific 

 it is widely distributed, as far south as California and Japan. 

 Bathymetrical distribution from the ebb-zone to 1880 m. 



VI. Family Amphiurid^ 



Disk generally distinctly scaled, sometimes Avith spines. A 

 pair of infra dental papillae on apex of jaw ; papillae on sides of 

 jaw contiguous or not contiguous with the infradental papillae. 

 A single series of square teeth, no tooth papillae. Two pairs of 

 tube -feet inside the mouth edge. Arms mostly very long, 



Fig. 117. — Amphiura Chiajei. Dorsal side. Nat. size. 

 (From Dam7iark"s Fauna.) 



slender, and very flexible. Arm spines short, outstanding. 

 Genital organs small, not in the shape of a single large mass at 

 each bursal slit. 



Most Amphiurids are characterised by their very long and 

 slender, very flexible arms (Fig. 117). They usually live 

 buried about a decimeter deep in the ground, with only the tip 



