236 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The spines are for the most part 2 or 3 mm. long but on the sides of the 

 petals are twice that length; the ventral primaries are very slender, about 10 

 mm. long, while the large dorsal primaries are a little stouter and if unbroken 

 (seldom the case in these preserved specimens) are 15-20 mm. long. Pedicel- 

 lariae are common but are all tridentate or triphyllous. The latter are rela- 

 tively large with valves .15 mm. long. The slender tridentate have their valves 

 .55-95 mm. in length but are not at all distinctive. The stout tridentate, with 

 valves .55-.70 mm. long, are more characteristic, for the outline of the blade 

 (PI. 146, fig. 20) is markedly more elongated than in the related species, and 

 strikingly different from the corresponding form in S. capensis, to which cali- 

 fornicus seems to be most nearly allied. 



The geographical isolation of this typical Spatangus is very striking. No 

 species of the genus occurs in the West Indies and none is known from the 

 Panamic region, nor from the American coast north of California. The nearest 

 species geographically is at the Hawaiian Islands but there is no particularly 

 close alliance morphologically with that species. Indeed the South African 

 species seems to be, as stated above, the nearest member of the genus structur- 

 ally, and were the specimens of californicus without locality labels, the bare 

 tests would probably pass as young examples of capensis. 



Station 2918. Off southern California. Bott. temp. 52.4°. 67 fms. 

 Fne. gy. s. 



Station 2 972. Off southern California. Bott. temp. 53.5°. 61 fms. 

 Gn. m. 



Station 2973. Off southern California. Bott. temp. 54°. 68 fms. Gn. m. 



Station 2974. Off southern California. Bott. temp. 53.2°. 73 fms. 

 Gn. m. 



Station 2977. Off southern California. Bott. temp. 56.5°. 45 fms. 

 Fne. gy. s., p. 



Bathymetrical range, 45-73 fms. Extremes of temperature, 56.5°-52.4°. 



Twenty-five specimens. 



Spatangus altus. 



Mortensen, 1907. Ingolf Ech., pt. 2, p. 131. 



This species is as yet known only from a single specimen in the Copenhagen 

 Museum, and supposed to be from the "China Seas." It seems to be a well- 

 marked species, distinguished from all the other members of the genus by the 

 composition of its subanal plastron. 



