234 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Key to the Species of Spatangus. 



Primary tubercles of dorsal side numerous, 150 or more in all the interambulacra 

 together. 



Subanal plastron more than twice as wide as high, with a re-entering angle on the 



upper side purpurew. 



Subanal plastron not nearly twice as wide as high, with no re-entering angle. 

 Only 2 pairs of ambulacral pores (with large tube-feet) included within 

 subanal fasciole on each side; petals II and IV tapering towards both 

 ends, more or less decidedly so proximally. 



Primary tubercles present in ambulacra between end of petal and 



ambitus raschi. 



Primary tubercles not present in ambulacra between end of petal and 

 ambitus. 



Subanal plastron more or less ventral in position its adoral margin 

 only .75-80 test-length from anterior end of test; 1 its length is 

 about .18 test-length and its width about .25 (measured out- 

 side fasciole) capensis. 



Subanal plastron posterior, its adoral margin .85-.88 test-length 

 from anterior end; its length is about .22 test-length and its 



width about .30 californicus. 



Three pairs of ambulacral pores (with big tube-feet) included within 

 subanal fasciole on each side; petals II and IV broad, not tapering 



towards ends even proximally alius. 



Primary tubercles of dorsal side few, fewer than 50 in all the interambulacra together. 

 Interambulacra 1 and 4 each with two, one or no primary tubercles. 



Test about half as high as long; usually 1 or 2 primary tubercles in inter- 

 ambulacra 1 and 4; 9 or 10 primary tubercles in interambulacrum 5; 



subanal plastron very oblique, nearly ventral paucituberculalus. 



Test more than half as high as long ; no primary tubercles in interambulacra 

 1 and 4; 1-9 primary tubercles in interambulacrum 5, subanal plastron 



more nearly vertical mermu. 



Interambulacra 1 and 4 each with 6-12 primary tubercles. - 



Sternum with little or no keel; subanal fasciole 1-1.5 mm. wide; color deep 



purple . hlikeni. 



Sternum with conspicuous keel; subanal fasciole, 1.5-2 mm. wide; color 



grayish lavender pallidum. 



Spatangus purpureus. 



O. F. Muller, 1776. Zool. Dan. Prod., p. 236. 



This is a European species occurring from Norway to the Azores and in 

 the Mediterranean Sea. Its bathymetrical range is 5-458 fins. 



1 Measured through one of the interambulacra 2 or 3 and not through 'I' 1 ' mote or loss depressed 

 ambulacrum III. 



2 In my Key to the species of Spatangus (1908. Bull. M. C. Z . 51, p. 806 the expreSBioo " lateral 

 ambulacra" occurs twice, concerning pCNCJhlbercytatut, liitkcrii, end poWdm, whore "lateral inter- 

 ambulacra " is intended. Such an error is most regrettable but will be remed i ed by the present key. 





