NO. 5 CLARK: ECHINI OF WARMER EASTERN PACIFIC 237 



most Stations were at Tepoca Bay, Sonora, where only two very young 

 specimens were taken and Tiburon Island, in the Gulf of California, in 

 16 fms, where 74 specimens were secured. The southernmost station was 

 at Santa Elena Bay, Ecuador, in 8-10 fms, but no specimens were taken 

 at either Cocos or the Galapagos Islands. 



Type. — Paris Museum ? 



Type locality. — "Habite — probablement les mers de I'Asie." 



Depth. — Shore to 20 fms. 



Specimens examined. — 165 specimens from 16 stations. 



Centrostephanus coronatus (Verrill) 



Plate 39, Fig. 10 



Echinodiadema coronata Verrill, 1867, p. 295. 

 Centrostephanus coronatus A. Agassiz, 1872a, p. 97. 



Mortensen, 1940, p. 314, pi. 36, figs. 7-10. 

 Compared with the preceding two species, this is a relatively small 

 sea-urchin, the largest known specimens being only 63 mm in diameter. 

 The largest of the 131 specimens collected by the Felero are only 45-50 

 mm with the primary spines about twice as much. As the spines are very 

 brittle, especially when dry, few specimens (even in the Vetera collec- 

 tions, notable for the fine condition of typical specimens in nearly every 

 species) show the handsome appearance of this sea-urchin in life. As in 

 Centrechinus the spines are finely verticillate and very acute but there is 

 no evidence that they carry poison at the tip as do those of Centrechinus. 

 A veiy interesting character of this Centrostephanus is the presence on 

 the uppermost interambulacral plates of short claviform spinelets the tips 

 of which are bright red purple. This color persists in most preserved 

 specimens but may be much duller and hence less noticeable than in life. 

 Mortensen discovered that these spinelets are never resorbed or replaced 

 by the long primary spines but the latter grow up around them and en- 

 close them without resorption. Young individuals of this Centrostephanus 

 are so similar to young examples of Centrechinus mexicanus that they are 

 often confused with them but there are three characters by which the two 

 species may be readily distinguished. The most important of these is the 

 presence of these brightly tipped claviform spinelets in Centrostephanus 

 which are never present in Centrechinus. A second distinctive character is 

 the presence of slender, blunt, light-colored spinelets on the five pairs of 

 oral plates around the mouth (in Centrechinus these plates may have 

 pedicellariae but never spinelets). The third difference is in the color of 



