SHORES OF THE CLYDE AND FIRTH. 
53 
the opposite angle. In a shell presently in my possession, 
measuring eleven inches in circumference, there are about 
420 holes in each band, giving in the ten the vast number 
of 4200, all proportionally set, and as beautifully rounded as 
though done by a practised hand with the point of the 
finest needle. On the same shell the spines number about 
2300. The tips of these appendages are invariably coloured 
similar to the shell, which may be dark red, senna brown, 
rose or purple tint, with the lower portion adorned with a 
lustrous coating of dark or sap green From tip to base 
they are marked all round with regularly divided fluted 
incisions, which add much to the handsomeness of their 
well-proportioned symmetry. 
A number of erroneous suggestions have been put forth 
regarding the use of the spines, but, as far as I am aware, 
no one has yet been able to determine their actual work ; 
but more of this hereafter. Piercing into the interior of the 
shell, it is found to be largely composed of a dark brown 
liquid, chiefly sea water, while several very fragile vascular 
tissues surround the jaws, from the top of which the stomach 
stretches to the vent on the crown above, giving the creature 
the peculiarity of having its food ascend 'ng to that organ, 
instead of descending ; just like a person swallowing their 
food standing upon their head. The infant urchin, bursting 
THE MOUTH OR MILL OF URCHIN. 
