ECHINOIDEA 339 



always with 3 valves, never 8-valved (as in atlantica) ; the 

 rostrate pedicellariae very slender (Fig. 199, 3) ; triphyllous 

 pedicellariae not characteristic. Colour in life mostly red-brown, 

 sometimes fading in alcohol. Reaches a size of ca. 70 mm. 

 length. 



It lives gregariously — often in immense numbers — on soft 



Fig. 201. — Larva of Brissopsis lyrifera. x 20. 

 (From Danmark's Fauna.) 



mud bottom, lying buried in the ground ; it fills its intestine 

 with the mud, subsisting thus on the organic substances and 

 small organisms (especially Foraminifera) found therein. The 

 breeding season is in the summer-time. The larva (Fig. 201) 

 differs from other known Spatangoid larvae in lacking the 

 postero-lateral arms. 



