LOBED URCHIN. 'Sncojxs grandit. KEYHOLE-URCHIN. ' Kncopt rubolatua. WHEEL-URCHIN. Rolula Rumpki 



disk which will represent the face of the clock, upon which are traced certain lines that 

 answer to the hands and figures. By rapid degrees, the disk expands and covers tht 

 gelatinous substance of the animal, and puts on hour by hour more of the Echinus as it 

 loses its former skeleton shape. The latter becomes rapidly covered by and absorbed into 

 the former, and in due time the framework of long slender rods, which might also be well 

 compared to an artist's easel, or the tripod stand of a theodolite, is converted into the 

 well-known globular Echinus, with all its complicated apparatus of spines, pedicillariae, 

 and walking organs. 



The reader may perhaps have noticed, that on inspecting a common Echinus, especially 

 from the interior, it exhibits in a very distinct manner its close alliance with the well- 

 known star-fishes. Take, for example, a common five-finger star-fish out of the water, 

 lay it on its back, and then gather all the five points together. Now, supposing the 

 creature to be dead, strip the skin from the rays, leaving it only adherent down the centre, 

 join the edges of the strips, and there is a very good imitation of the Sea-urchin. 



THE two curious specimens represented in this illustration also belong to the Shield- 

 urchins. 



The KOTULA, so called because of its wheel-like shape, is nearly as flat as a piece of 

 money, and has a very slight elevation in the centre. It is remarkable for the very deej 

 teeth into which one side of the disk is cut, giving the creature an aspect as if it were 

 cog-wheel in process of manufacture. The colour of this species is mostly greyish slat 

 above, and dull white below. The under surface is veined over its whole extent, al 

 the veinings radiating from the centre. The colour of this Rotula is, however, extremely 

 variable. 



