THE SECRETS OF THE SEA 327 



it was at once seen that though much alike they 

 belonged to different species. So Mr. Henderson 

 renamed the Pacific shell in honor of Dr. Dall. 

 The Florida Haliotis is quite attractive, the outer 

 part being waxy yellow with patches of orange and 

 the interior a brilliant pearl. As only this speci- 

 men dredged by Mr. Henderson and a few other 

 fragments obtained by him are known it is one of 

 the rarest shells in the world. Since it was ob- 

 tained at a depth of ninety fathoms and all the 

 dredging on this plateau has only yielded so few 

 of them it is likely that it will always be rare. 



Many of the shells of these deep sea mollusks 

 are richly iridescent; others have a delicate 

 shagreen, caused by an outer pearly layer of 

 minute knobs or spines which gives them their 

 sheen. Among shells so marked were several 

 small cockles {Cardium peramabUe), which in per- 

 fect condition looked like pearls. Some of the 

 Gazas, which belong to the Trochus family, are 

 most exquisite gems, and well might be worn as 

 ornaments. 



Perhaps the most astonishing thing we took was 

 an Ophiuran or "brittle star," one of the Echinp- 

 derms, and related to the starfishes. The Ophi- 



