ECHINOIDEA 



31' 



the Azores, Cape Bojador and the Mediterranean, whereas all 

 records of its occurrence in the West Indian seas are due to a 



1 2 



Fig. 183. — Larva of Echinocyamus pusillus. (From Danmark^s Fauna.) 



1. I. stage, lateral view ; only the skeleton of the iipturniug side has been drawn 

 (after Theel). 2. II. stage, seen from the oral side. 1, x ca. 100 ; 2, x 35. 



confusion with Ech. grandiporus. 

 from lower tide limit to 1250 m. 



Bathymetrical distribution 



IV. Order. Cassiduloidea 



Test elongate or round, not flattened. Mouth central or 

 anterior, anal opening posterior, often in a depression, or on the 

 under side. No gills or gill- cuts at peristomial edge of test. No 

 internal supporting system of pillars. No dental apparatus. 

 Ambulacra simple or petaloid on upper side and often also 

 widened at the mouth. Posterior interambulacrum not different 

 from the others on the oral side. Tubercles imperforate. Spines 

 small, those on the lowermost interambulacral plate usually 

 somewhat larger, flattened, bending over the mouth, which is 

 thus covered bj^ 5 fan-shaped groups of spines. No fascioles. 

 Tube - feet confined to the ambulacra ; oral tube-feet not 

 penicillate. Pedicellariae small, usually the tridentate, ophi- 

 cephalous, and triphyllous form present. Sphaeridia present, 

 placed in more or less closed grooves. 



One family represented in British (and European) seas. 



