NO. 3536 DECAPOD CRUSTACEANS — CHACE 653 



male only; dactyl with five to seven low tubercles on ventral margin. 



Male abdomen and gonopods as figured. 



Color: In ethyl alcohol, carapace vnih rusty to orange-red re- 

 ticulated mottling on grayish background; elevations cream colored. 

 Chelipeds with dark, rusty red patch near distal end of upper surface 

 of merus and reticulations of same color on carpus and on inner and 

 outer surfaces of hand; hght orange-red mottling on upper surface of 

 hands and in two bands on fingers. Speckels of red on ambulatory 

 legs and on ventral surfaces of crab. 



Measurements: Carapace of male holotype, 11.3 mm. long in mid- 

 line, 13.2 mm. long to tip of rostral spine, 9.7 mm. wide between 

 branchial margins, 10.7 mm. wide between tips of lateral spines. 

 Carapace of ovigerous female paratypes, 5.8 and 8.2 mm. long in 

 midline, 7.0 and 9.2 mm. long to tips of rostral spines, 4.3 and 6.8 mm. 

 wide between branchial margins, 5.0 and 7.6 mm. -wide between tips 

 of lateral spines. 



Remarks: Pisa sandaehelenae bears a faint resemblance to P. 

 carinimana Miers, 1879, from West Africa and the Canary Islands, 

 but it is readily distinguished by the much stronger preocular and 

 antennal spmes, the sahent posterolateral angle of the supraocular 

 eave, the larger intermediate supraocular tooth, the more uneven 

 carapace, and the more numerous spines on the branchial margins.^ 



Distribution: Known only from the type locahty off Rupert's Bay, 

 St. Helena, where it was represented only in the last of the five collec- 

 tions made from the buoy and cable at that location. 



Distribution 



The distribution of the 23 species of decapod crustaceans (fig. 15) 

 does not conform exactly with the distribution patterns of St. Helena 

 fishes (Cunningham, 1910, and Cadenat and Marchal, 1963), mollusks 

 (E. A. Smith, 1890), and echinoderms (Mortensen, 1933). CoJman 

 (1946, p. 279) concluded from the studies published prior to 1946 that 

 "In each case the principal links are mth the West Indies first, and 

 secondly, ^ith the Mediterranean and north-east Atlantic, while there 

 is only a sUght connection with South Africa." Cadenat and Marchal 

 (p. 1307) state that "les affinites de cette faune sont tres nettement 

 plus antiUaises que ouest-africaines." On the contrary, the decapods 

 seem to be more closely allied to the West African than to the East 

 American faunas. Excluding the six decapods that are found in 



2 Pisa sandaehelenae seems to differ from the closely related P. calva Forest and 

 Guinot, 1966 (p. 99, figs. 10, lla-f, 13), in its divergent rostral spines, more 

 salient posterolateral angle of the supraocular eave, and more angularly sinuous 

 shaft of the male gonopod. 



