NO. 6 ECHINOID DISTRIBUTION AND HABITS — KIER, GRANT 5 1 



Measurements. — 



Length Width Height 



40.0 39.5 27.0 

 36.9 35.4 28.9 

 21.6 20.6 17.0 



21.1 19.6 16.2 



Shape. — Test subglobular, nearly as wide as long with greatest 

 width near center, test high, with height 70-80 percent of length ; an- 

 terior margin indented, posterior slightly truncated, margin slightly 

 angular particularly in larger specimens ; in side view anterior profile 

 sloping steeply, posterior nearly vertical, indented at and immediately 

 below periproct ; node present on most interambulacral plates on 

 adapical surface, nodes on interambulacral plates where crossed by 

 fasciole ; adorally test slightly convex, plastron more convex. 



Apical system. — Central to slightly posterior to center; depressed 

 below interambulacra ; four genital pores (pi. 13, fig. 5), anterior pair 

 much smaller than posterior, circular to slightly elongated into inter- 

 ambulacra; system ethmolytic with madreporite extending consider- 

 able distance posterior to posterior oculars, very narrow where passing 

 between posterior genitals; ocular plate of ambulacrum III small, 

 higher than wide, deeply inserted between genitals 2 and 3 ; other 

 oculars large, approximately equal in size, roughly pentagonal. 



Ambulacra. — Ambulacrum III deeply depressed with groove ex- 

 tending over ambitus to peristome ; adorally, bottom of groove slightly 

 concave, sides sloping, not vertical ; adapically sides steep, almost ver- 

 tical ; pore-pairs arranged in simple regular series near edge of 

 ambulacral groove (pi. 13, fig. p) ; pores oblique with inner pore of 

 each pair more anterior, smaller, and more elongate than outer ; pores 

 near apical system very small, increasing in size anteriorly, last 2 or 3 

 pore-pairs very small; 15 pore-pairs in poriferous zone in specimen 

 21.1 mm. long, 18 in specimen 40.0 mm. long; pores beyond axis ex- 

 tending longitudinally to ambulacrum III; petals II and IV long, 

 extending f distance from apical system to margin, curved distally 

 with greatest width § distance from apical system to end of petal ; both 

 pores of each pair approximately same size, outer pore more slitlike 

 than inner ; interporiferous zone narrow, approximately same width 

 as distance between pores of pore-pair ; 22 pore-pairs in each porif- 

 erous zone in specimen 21.1 mm. long, 26 in specimen 40.0 mm. long; 

 posterior petals V and I short, extending less than ^ distance from 

 the apical system to the margin, one-half as long as petals II and IV, 

 greatest width near midlength of petal ; interporiferous zones approxi- 



