90 THREE CRUISES OF THE " BLAKE." 



fan-shaped spines, it would have been unhesitatingly placed in 

 the genus Dorocidaris. If the isolated huge fan-shaped radioles 



Fig. 349. Dorocidaris Blakei. f . 



nearly identical in shape with those of the Jurassic Rhabdoci- 

 daris had alone been collected, few palaeontologists would have 

 hesitated to refer them to that genus. 



Another interesting type of deep-sea Cidaridse allied to ter- 

 tiary forms is Porocidaris (Fig. 350), which is characterized by 

 the peculiar serrated spines found near the mouth. 



We first dredged off Havana, and subsequently in all parts of 

 the Caribbean, a fine species of Salenia (Fig. 351), a genus once 

 very common in the Jurassic and cretaceous seas. The first 

 living species of the genus (Fig. 352) was dredged by Pourtales 



Fig. 352. Salenia varispina. 



off Double-headed Shot Key, in 315 fathoms. The " Blake " 

 found it to be a characteristic species of the Caribbean abyssal 

 fauna. This genus is characterized by the presence of a large 



