162 CIDARITES. 



The Echinus miUaris is the least of our native Egg- 

 Urchins, commonly not measuring more than three-fourths 

 of an inch across, by three-tenths high ; but it sometimes 

 attains the diameter of an inch and three-fourths, and a 

 proportionate height, its form always being much de- 

 pressed, nor does it vary in that respect like other Ur- 

 chins. Its body is rose colour, with white tubercles ; 

 all the primary spines, which are often nearly thrice as 

 long as the secondaries, are purple, with yellow bases, and 

 the secondaries yellow. On large examples the primary 

 spines are not so long in proportion to the others as on 

 small ; and there is a variety which has all the spines very 

 nearly equal in size, and very thick. Usually they are 

 long, tapering and slender, and always shining, which lustre 

 is derived from the broad smooth ridges on them, and the 

 striae not crossed by transverse striations. When the 

 spines are rubbed away, the shell presents a very pretty 

 radiated appearance in consequence of the tubercles of the 

 primary spines being much larger and more prominent than 

 the other tubercles, and closely placed together, forming 

 twenty white rays on the pink body, there being one large 

 primary tubercle, and a number of small secondary ones 

 on each ambulacra! and inter-ambulacra] plate. The 

 tubercles are depressed polished spheroids, mounted on 

 broad prominent bases. On each of the ovarian plates are 

 four tubercles, three being placed on the upper edge, so 

 that there is a ring of tubercles round the anus. On each 

 inter-ovarian plate there is one small tubercle. The ovarian 

 holes are large, somewhat oval, and surrounded by a dis- 

 tinct prominence or ring. The madreporiform tubercle is 

 triangular, prominent, and very porous. The ambulacra 

 are undulated in consequence of the rows of pores being 

 arranged almost vertically. Each pair of pores is placed 



