CLYPEASTER. 23 



petal 22 mm. long); primary spines slightly and uniformly tapering to a blunt 



point; color more or less dark, reddish brown ........ rosaceus. 



Test very evenly convex above, the petals scarcely at all elevated; pore-pairs much 

 less numerous (thirty-nine on each side, in an unpaired petal 37 mm. long); 

 primary spines acute, often enlarged just below tip; color light reddish .... pallidal. 



Margin of test more or less distinct, its thickness usually less than .20 and often less than 

 .10 test-length; height of test seldom exceeds .30 test-length. 

 Test about as wide as long, usually distinctly pentagonal with more or less concave 

 sides, but sometimes the ambitus is circular; between ambitus and distal end 

 of petals, the test is flat and its height there is only .03-08 test-length; lower 

 surface of test not at all concave. 

 Petals, especially unpaired one, broadly open at distal end. 



Petals rather broad, the unpaired one being more than half as wide as long, 

 the others somewhat narrower; poriferous areas parallel or somewhat 

 diverging; tuberculation of test rather coarse (sixty-sixty primary tu- 

 bercles to each sq. cm. of surface, aborally, near margin); margin 



somewhat swollen, its thickness about .08 test-length ravenelii. 



Petals narrower, width of unpaired one .40-.50 its length; poriferous areas 

 converging distally; tuberculation of test less coarse; margin thin, not 



at all swollen, its thickness about .03-04 test-length europacificus. 



Petals narrow, more or less closed at distal end. 



Test moderately high (v.d. = .15-20 test-length) with somewhat swollen 

 margin (thickness = about .08 test-length) ; petaloid area rather more 



than .60 test-length audouini. 



Test very flat (v.d. hardly .15 test-length); margins not swollen, their 



thickness about .04 test-length; petaloid area .45-.55 test-length . . . rarispinus. 

 Test distinctly longer than wide, ambitus usually rounded but often pentagonal 

 with nearly straight sides. 

 Test rather high (v.d. = .20-.35 test-length) with thick margins (thickness 

 = .09-.22 test-length) ; aboral surface inclining upward more or less uni- 

 formly from margin (not in reticulatus) ; lower surface concave or (in spe- 

 ciosus and usually in japonicus) distinctly sunken only near mouth; 

 tuberculation rather coarse (finer in australasiae) the ridges between 

 pore-pairs of unpaired petal with only 4-6 (more in australasiae) or 

 fewer primary tubercles. 

 Lateral petals more or less widely open. 



Tuberculation rather coarse; pore-pairs in unpaired petal numerous 

 (more than forty-five in a petal 33 mm. long), the ridges be- 

 tween narrow, each with a single series of four to six primary 

 tubercles. 

 Test high (about .25 test-length), markedly concave beneath; 



color light yellowish brown ochrus. 



Test more flattened (about .20 test-length), slightly concave 



beneath; color deep purplish brown or blackish purple . . speciosus. 

 Tuberculation finer; pore-pairs not numerous (only about 45 on each 

 side in a petal 56 mm. long); ridges between broad with 6-12 



primary tubercles, often in double series australasiae. 



Lateral petals (at least anterior pair) more or less completely closed. 



Size large, length up to 100 mm. and more; width exceeding .80 



