•54 bulletin cf the Jhatural History Society. 
Figure. (K) p. 107, (0) pi. Xle, (Q) pi. XXXV. 
Distribution, (a) General ; — Low-water mark to 888 
fathoms. Almost cosmopolitan. Atlantic coast of North 
America from New Jersey to Labrador. Both sides of the 
Pacific Ocean. Australia, and possibly the Red Sea and India. 
{h) In N. B. waters; Grand Manan, low water on sandy 
shores, very common, Stimpso7i, (D); Eastport, low water, Ker- 
rill, (N); Chamcook harbor and Hospital Island, abundant, 
Ga^iong, (X); Shediac and Gulf of St. Lawrence, Whiteaves (P). 
Abundant on southern coast alnrost everywhere in sand just 
below low-water mark. 
This Ecliinoderm is almost described, in so far as Us general appear- 
ance is concerned, by its two English names alone. In outline it is 
nearly circular, is quite flat upon its lower side and only gently convex 
upon its upper, being in profile not unlike a strung bow. It grows to a 
diameter of three inches, is reddish brown in color and covered with 
crowded very short slender spines which make it appear, when first 
taken from the water, as if covered with velvet. The dead and bleached 
shells sometimes found upon the shore but easily prepared, show the 
plates of which it is made up and their homologies with those of the 
common sea-urchin, together with the distribution of the short ambula- 
cral feet. The latter are confined upon fhe under side to five radiating 
furrows which branch towards the ends. Upon the upper side they 
are modified and enlarged to form branchial or gill-like appendages, and 
the pores through which they pass are arranged in a regular rosette of 
five petals, which is very conspicuous in the dead shell. The teeth are 
not visible externally, though they may be seen through the spines 
which protect the mouth. 
The Cake-urchin lives always upon sandy bottoms and usually in 
shallow water. It creeps along very slowly by means of its many tube- 
feet just beneath the surface of the sand or half covered by it, feeding 
upon the minute organisms, both animal and vegetable, which the sand 
contains. It is itself eaten by some fishes, espeeially flounders. It has, 
according to Prof. Verril (Q), a certain limited direct value to man. 
“The fishermen on the coast of Maine and New Brunswick sometimes 
prepare an indelible marking ink from these ‘ sand-dollars ’, by rubbing 
off the spines and skin, and, after pulverizing, making the mass into a 
thin paste with water.” It is always an interesting form to all who 
chance to meet with it, on account of its shape and pretty markings. 
In its development it passes through a metamorphosis similar to that 
of the ordinary sea-urchin, having a Pluteusnot unlike the latter. [See 
Plate, Fig. 14a.] From a point near the mouth the adult sea-iuchin 
buds off, gradually absorbing the substance of the Pluteus as it grows. 
