CHARACTERISTIC DEEP-SEA TYPES. SEA-URCHINS. 



95 



to be its normal form and attitude. It is quite dangerous to 

 handle these specimens when alive, the wounds they inflict with 



Fig. 359. Asthenosoraa hystrix. $. 



their numerous minute sharp stinging spines producing a decid- 

 edly unpleasant sensation, accompanied by a slight numbness. 

 The sting is fully as painful as that of Physalia. These modern 

 Echinothuriae were 

 subsequently found 

 very abundant at 

 moderate depths. 

 The "Challenger" 

 dredged a gigantic 

 species from this 

 group, measuring 

 no less than 312 

 mm. in diameter. 



The spines of the 

 lower surface are 

 shod with a pecu- 

 liar hoof -shaped 

 tip ; on the test are 

 sheathed spines un- 

 like those Of any Fig. 360. -Phormosoma placenta, f. 



