l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 145 



which this area can be seen this distance averaged 13.1 percent of 

 the length, with a standard deviation of 0.29. In the nominate sub- 

 species (using 59 specimens) this distance averages 11.2 percent of 

 the length, with a standard deviation of 0.69. Even though there are 

 so few fossil specimens the difference between this distance between 

 the primary ambulacral tubercles is highly significant as shown in a 

 scatter diagram (text fig. 11) and by biometric analysis. Using the 



10 1 



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a. < 



uj & 



g CO 

 o g3 



g'< I 



en 



Q 









°0 



u a B 









** 







a 



O ° a B ° D a 

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rrma 



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a RECENT 



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o CALOOSAHATCHEE 

 * TAMIAM! 



10 



20 30 40 50 



LENGTH IN MILLIMETERS 



60 



70 



Fig. 11. — Lytechinus variegatus (Leske). Distance between primary ambu- 

 lacral tubercles relative to length of test in specimens of L. variegatus variegatus 

 (Leske) from the Recent and specimens of L. variegatus plurituberculatus Kier, 

 new species, from the Caloosahatchee and Tamiami formations. 



procedure recommended by Burma (1948, p. 731) and followed by 

 Kier (1957, p. 86) a value of 12.6 was found for the difference in 

 the means of the distance between the primary ambulacral tubercles 

 in the two populations. Since a result of 3 or more is almost certainly 

 significant, with the degree of probability increasing greatly with the 

 increase of this number, it is evident that these populations are signifi- 

 cantly different in this character. In the two Tamiami specimens the 

 distance between the primary tubercles is less than that in the Caloosa- 

 hatchee specimens but more than in the nominate subspecies, with an 

 average of 12.15 percent of the length and a standard deviation of 0.07. 

 Although these differences in the number and arrangement of the 



