366 Annals of tlie South African Museum. 



SEA-URCHINS. ECHINOIDEA. 



Sea-urchins form a proportionately large part of the South Afri- 

 can echinoderm fauna, for while the brittle-stars of the region are 

 only about four per cent of the known species, the echini are nearly 

 ten per cent of the known forms. This is in keeping with the 

 results from the THETIS and ENDEAVOUR collections, about southern 

 Australia, which show that Echini form a relatively large propor- 

 tion of the echinoderms of that region. The fact as regards South 

 Africa may be expressed in this way: that, whereas echini make 

 up only about eleven per cent of the echinoderm fauna of the 

 world, in South African waters, they make up more than twenty 

 per cent of the echinoderm fauna as now known. And yet, cu- 

 riously enough, south of Mozambique, not more than two or three 

 sea-urchins are known to occur along shore, and only Pareckinus 

 angulosH* is at all common on the Cape Colony coast. 



Doderlein, in his list mentioned previously (see p. 2212), gives 25 

 species of Echini as occuring in water under 278 fins., but one of 

 these (Protocentrotns annuldtus) is synonymous with another (Pare- 

 cliinus angulatus) and one (Temnoplearus reevesi) is not accepted for 

 this report (see p. ). The collection from the South African 

 Museum contains 240 specimens of 30 species, (3 apparently new to 

 science) of which only 13 are in Doderlein's list. There are howe- 

 ver 2 species hitherto known from Mozambique and 1 from Natal, 

 and a deep water species from 46 miles off Cape Point, which were 

 not included by Doderlein in his list and are not in the collection 

 before me, so that 44 species are included in the present report. 



Of these 44 species, 23 are truly littoral, occurring in water less 

 than 20 fms. deep, while only 4 are strictly abyssal, living nor- 

 mally beyond the 600 fms. mark. Of the remaining species 16 are 

 continental and one (Spatagobrissus) is either littoral or continental 

 but its exact habitat is unknown. 



Of the 23 species known to be littoral, only 2 are endemic, a 

 surprisingly small proportion. Of the remaining 21 species, 6 are 

 characteristic of the western Indian Ocean, while 13 are widely 

 distributed Indo-Pacific forms; one of the remaining two has been 

 known hitherto only from Liberia, while the other is cosmopolitan. 

 None of the littoral species is known from either South America or 

 the southern coasts of Australia. It is noteworthy that 8 of the 23 

 littoral echini are not known from south of Mozambique and there 



