no. 5 



TERTIARY ECHINOIDS FROM FLORIDA — KIER 



II 



SYSTEMATICS 



ARBACIA CRENULATA Kier, new species 



Plate 1, figures 1-5 ; text figures 3-7 



Diagnosis. — Species characterized by crenulated ornamentation on 

 plates. 



Material. — Thirty-one specimens most of which are extremely 

 well preserved with all the ornamentation visible. 



Shape. — Medium size, varying from a horizontal diameter of 11.8 

 to 42.0 mm ; moderately high, with height 40 to 50 percent of diame- 

 ter, height-diameter ratio constant throughout growth (text fig. 3). 



CO 



en 



Hi 



H 



ui 



2 



2 



z 



H 



X 



o 

 ixi 



X 



30- 



20 



10 



4+ 



++ 



•rft 



10 20 30 40 



DIAMETER IN MILLIMETERS 



Fig. 3. — Arbacia crenulata Kier, new species. Height of the test relative to the 



diameter. 



Apical system. — Preserved in 21 specimens; all oculars exsert in 

 all specimens (text fig. 4) ; oculars generally pentagonal, small usu- 

 ally without tubercles ; genital plates large with genital pore in center 

 of each plate; periproct elongate diagonally from interambulacra 

 3 to 1, at greatest width between 13 to 17 percent of horizontal 

 diameter of test. 



Ambulacra. — At ambitus one-half width of interambulacra; por- 

 iferous zones straight from apical system to near margin, arcuate 

 around large tubercles at margin, greatly widened adorally; adorally 

 tubercles so large that pore pairs perforate bosses ; ambulacral plates 

 compound, trigeminate ; in each poriferous zone 35 pore-pairs in 

 specimen 13.8 mm in diameter, 42 in specimen 19.7 mm in diameter, 



