124 



ROBERT TRACY JACKSON ON ECHINI. 



and 0.5% all oculars insert. Two specimens are aberrant variants, one with I, V, II and one 

 with V, IV, II insert (text-fig. 196, p. 169) ; as genitals 5, 1 are fused, this may be considered 



Text-figs. 123-127. — Ocular plate arrangement in Tripricusles esculcnlus (Leskc). All figures X 2.7. 



123. Bermuda. Diam. 145 mm. R. T. J. Coll., 896. Ocular I only insert, an extreme arrested variant, but the largest 

 specimen seen in the species. 



124. Nassau, Bahamas. Diam. 100 mm. R. T. J. Coll., G75. Oculars I, V insert, an arrested variant for the West 

 Indies. 



125. Nassau, Bahamas. Diam. 95 mm. R. T. J. Coll., 677. Oculars I, V, IV insert, the typical character for the 

 West Indies. 



120. Nassau, Bahamas. Diam. 81 mm. R. T. J. Coll., 653. Oculars I, V, IV, II insert, a progressive variant (p. 94). 

 127. Bahamas. Diam. 95 mm. R. T. J. Coll., 676. All oculars insert, an extreme progressive variant. 



an incomplete I, V, IV, II. The species is abundant in Bermuda and attains a" large size. 

 The range of variation of Bermuda specimens is similar to that of the southern form, but the 

 percentages are radically different. 



Tripneustes esculefitus from the West» Indies and Florida as regards oculars is much more 

 progressive than the Bermuda form. I have divided the specimens into an immature develop- 



