294 ECHINUS GRACILIS. 



intermediate spaces forming brilliant white or straw-colored hands. In one 

 of these white hands is placed the poriferous zone, and each primary row of 

 tubercles is placed in a similar hand at the junction of the points of the green 

 lozenges. Thus the test is divided into twenty bands alternately green and 

 white ; the poriferous zones, and two principal rows of tubercles being sepa- 

 rated by these dark green lozenges, giving the test a most graceful pattern 

 of coloration. The ahactinal system is compact and circular ; the shape of 

 the genital plates is a pointed pentagon somewhat as in E. melo, while in 

 Flemingii they are heptagonal. The madreporic body is reduced to a narrow 

 band across the genital plate. The anal system is made up of a large num- 

 ber of small plates. The ten large plates of the buccal membrane are quad- 

 rangular with rounded corners, carrying stout pedicellarhe similar to those 

 of E. melo. The position and general arrangement of the tubercles is similar 

 to E. melo ; the large tubercle is placed in the centre of the interamhulacral 

 plate, which carries in addition short horizontal rows of two or three minute 

 tubercles, tin 1 row near the horizontal suture being the most prominent In 

 the ambulacral zone the main tubercle has a similar position ; the small 

 tubercles are placed close to the median suture, and form irregular vertical 

 rows. Two kinds of pedicellarise are scattered over the whole surface of the 

 test, supported upon distant miliaries, both in the ambulacral ami interam- 

 hulacral areas. The short-stemmed, thick-headed ones are similar to those 

 of E. melo. The long-stemmed have a triangular, sharp elongate head at the 

 extremity of a very slender stem, with wide arched openings. The distance 

 between the milled ring and the articulating surface of the shaft of the spine 

 is greater than in either of the allied species of Echinus. 



In younger specimens the smaller tubercles of the interamhulacral spaces 

 form irregular vertical lines, two on each plate; the miliaries are less numer- 

 ous, the anal plates larger and fewer in number, and the white hands of the 

 poriferous zones better marked ; the ten buccal plates are thickly studded 

 with stout pedicellariae. 



In still younger specimens, measuring from 10 nun to 15 mm , the elegant 



