COMMON SAND-STAK. 23 



OpMura bracteata, Flem. Brit. Anim. p. 488. Johnston, in May. Nat. Hist. 



VIII. p. 465, f. 41. 

 OpMura Aurora, Risso, Eur. Merid. V. p. 273, f. 29. 

 OpMura arenosa, Leach, Zool. Misc. II. p. 58. 

 Stella lacertosa, Link, p. 47, tab. ii. No. 4. 



Professor Agassiz very properly proposed the generic 

 separation of the lacertose from the worm-armed Ophiurse. 

 The habits and characters of each are equally distinct. 

 The true Opliiura live in sandy places. Their preference 

 of such a locality is amusingly enough accounted for by 

 Reaumur, who tells us that, because they are so fragile 

 they are not able to live among rocks, and therefore in- 

 habit sand: — a true closet reason; had he only walked 

 to the sea-shore, he would have seen the Ophiocomce, which 

 are far more brittle, in abundance among the rocks, moving 

 about in perfect safety. Natural, however, as is the ge- 

 nus, the character, as restricted by Professor Agassiz, is 

 quite inapplicable, and might serve as a warning against 

 the dangerous practice of defining genera of radiated ani- 

 mals without reference to their habits and appearance 

 when alive. " Disk much flattened ; rays simple, squa- 

 mose, bearing very short spines adhering to the rays." 

 The disk is only flat in the dried specimen. When the 

 animal is alive, it pouts it out so as to make it very convex ; 

 in fact, the disk is much more moveable than in the next 

 species. The spines are quite as long as those of many 

 species of Ophiocomee, and are only appressed when the 

 animal is dead : when it is alive, they stand out as in a 

 Brittle-star ; but as they are placed in a different manner 

 on the lateral ray-plate, — or rather as the lateral ray-plates 

 are somewhat imbricated, — they naturally close on the 

 ray when the animal has no power over them. The 

 cirrhi, which are placed between the rows of spines, are 

 long, simple, and very flexible. Round the mouth there 



