NO. 5 CLARK: ECHINI OF WARMER EASTERN PACIFIC 345 



Spatangus callfornicus H. L. Clark 



Plate 69, Figs. 78-79 



Spatangus calif ornicus H. L. Clark, 1917, p. 235, pi. 156, figs. 1-3; pi. 



157, fig. 10. 



This interestingly isolated Spatangus is represented in the Velero col- 

 lection by 240 specimens from 47 stations, ranging in size from 

 21x18x12 mm to 86 x 79 x 43 mm. The general form is ovoid, more or 

 less flattened both above and below, but some individuals are more ellip- 

 soidal though flattened on the oral side. Occasionally the breadth equals the 

 length and in such individuals the height may be less than half the breadth. 

 The color shows a considerable diversity and is difficult to describe. 

 Theoretically the test is a rich deep purple and the spines more or less 

 nearly white, but often the test is deep red brown or, on the other hand, 

 a clear gray without hint of red or purple. Occasionally the test is light 

 with dark blotches and such specimens have a very diflFerent appearance 

 and are much more nearly handsome than the dull purple one. The spines 

 may be cream color or yellow or orange brown but are usually quite in 

 contrast with the test. 



The development of the very young into mature individuals affords 

 some very interesting and puzzling stages which are confusing because of 

 the resemblance to Palaeotropus. The striking feature of these stages is the 

 simple nature of the ambulacral pores which are single and not paired. In 

 some very young individuals only the pores at the apical end of the ambu- 

 lacra are clearly present and each is single. There is thus no well-marked 

 petal, only a double series of pores at the upper end of each ambulacrum 

 as in Palaeotropus. With increasing age and size the older pores elongate 

 horizontally and become two pores united by a short groove essentially 

 like the pore-pairs on each side of the petal in Spatangus and its allies. This 

 alteration in the appearance of the petals does not take place at the same 

 stage of development in all young, but usually occurs very soon after the 

 assumption of the spatangoid form so that most individuals 8-10 mm long 

 have normal petals of 2 columns of double pores. Rarely, individuals as 

 much as 15-20 mm long, have only single pores in each side of the ambula- 

 crum, and the absence of petals in such specimens is very puzzling and may 

 cause them to be referred to Palaeotropus. (See Fig. 76.) 



Distribution. — ^The Velero did not take Spatangus until February, 

 1936, when specimens were secured in 100-120 fms, south of Coronados 

 Island in the Gulf of California. A little later specimens were dredged in 

 165 fms off San Francisquito Bay and in 100 fms a bit nearer the mouth 



