AMONG THE SEA-URCHIXS. 13 



Echinus left high and dry. He had evidently been hunting for 

 prey, and had not calculated the depth of the receding tide, for 

 the sucker feet are only available when under water. 



The outside muscular coat is full of nerve-tissue of great 

 power. This is especially seen in the Purple Heart Urchin 

 {Sj>afa?igus purpiireiis\ where the lower spines are very long, 

 with which the creature is enabled rapidly to clear away the sand 

 in every direction and quickly sink out of sight and danger. We 

 took several of these handsome purple species one day when out 

 with a fishing trawler. They are oval-shaped and rather flat 

 in appearance, measuring from four to five inches in their longest 

 diameter. The markings show very beautifully when the shell is 

 cleared of its spines, etc. 



We were also fortunate in securing two specimens of the 

 Brissus lyrifer, which is also heart-shaped, with smaller spines, but 

 having a most curious dorsal impression engraved on the shell, 

 from which it is called the Fiddle Heart-Urchin. The figure of 

 these hairy sea-eggs, as the sailors call them, is well shown in our 

 centre illustration on Plate I., where one-half of the shell is 

 denuded of its spines, in order to show the arrangement of pores, 

 taking something like the form of a cross, from which the tube 

 feet proceed. In Spatangiis they take the form of a leaf, as they 

 are similarly arranged in the centre of Clypeaster (Fig. i, D). 



The small Heart Urchin {Amphidotus cordatus) inhabits the 

 sand at the bottom of the sea in our shallow bays. It is very 

 often found thrown up by the receding tide along the shores at 

 Blackpool and Southport, appearing white and very brittle when 

 thus bleached and denuded of its spines ; but a perfect specimen 

 is sometimes found covered with its hair-like spines, which vary 

 in form. They are all very slender and curved, some being flat- 

 tened towards the tip, the whole appearance being very silky and 

 glittering when dried. We will take up one of these sea-eggs 

 denuded of its spines, and minutely examine it with the micro- 

 scope with reflected light. The bosses or tiny nipples shine with 

 sparkling brilliancy like polished glass. The under-part of the shell 

 appears to be covered with a beautiful network of curved oval pits 

 or little depressions which surround these glassy knobs. This is 

 a beautiful provision of Nature, giving the thin muscular flesh, 



