64 THE SEA URCHIN. 



whole dental apparatus, consisting of thirty pieces, forms 

 a sort of pentagonal pyramid, and is known by the fanciful 

 name of " Aristotle's Lantern." 



Before leaving the Sea Urchin, we must notice the 

 remarkable fact that in every geological epoch from the 

 Silurian downward, remains of Echinoderms are to be found, 

 though the species increase in number as we approach the 

 present epoch. Now they are distributed over a very large 

 area of the earth's surface, and at various ocean depths. 

 During the voyage of the Challenger specimens were dredged 

 from a depth of over 2,000 fathoms. 



With a list of the urchins found in our own seas — and 

 for which in its complete form I am indebted to Mr. J. Sinel, 

 of Jersey, — I will bring this imperfect sketch to a close, with 

 a hope, however, that with all its faults, I may have suc- 

 ceeded in interesting some at least in this humble but 

 wonderful creature, on the structure of which it has been well 

 said, the skill of the Great Architect is seen not less than in 

 the building up of the universe. 

 Echinus sphcera (Common Egg Urchin), common throughout the 



Channel Isles, both the type and varieties. Var., E. melo, 



E. ventriculosus. 

 E. miliaris (Purple-tipped Egg Urchin), common throughout Channel 



and Channel Isles. 

 E. Jlemingii, rare in Channel, Herm, Jethou and Jersey. 

 E. lividus, or E. purpureus, Herm, Guernsey and Sark (not Jersey). 

 E. brevispinosus, or E. esculentus, or Spcerechinus granularis, rare in 



Channel, frequent in Sark, and not very rare in Jersey. 

 Spatangids : — 

 Echinocyamus pusillus, Herm, and Guernsey. Not very common. 

 Spatangus purpureas, fine at Herm, and in Great Russell, Guernsey, 



and rare in Jersey. 

 Echinocardium, Herm, off Sark. Not common. 



