PLATE CLX. 



.An Echinus, or sea egg, of very singular appearance, the whole 

 surface of the dorsal region being tessellated or divided into hex- 

 agonal spaces, formed by the obtuse terminations of the clavated 

 spines. Those spines, as will appear from the figure, approximate 

 very closely to each other on the upper surface, and being of an 

 uniform height, present very nearly a level surface, but the length 

 of those on the descent towards the margin is greater, and those 

 which surround the margin of the lower disk are yet longer than the 

 latter. This is the appearance of the dorsal surface ; the Echinus 

 inverted so as to shew the inferior surface presents an aspect much 

 resembling an expanded multipetalous flower, the coralla being 

 formed of the marginal series of spines, and the remarkable apparatus 

 of its five-rayed mouth, rising in the centre like the stigma of certain 

 blossoms, in addition to the numerous filamentous spines by which 

 it is surrounded, contributing materially to render its resemblance 

 more complete. 



The colour of this curious production of the marine element is 

 a deep blackish violet with a velvetty surface. It is an inhabitant 

 of the Indian seas. 



