304 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 11 



Diagnosis: Length up to about 10 cm. Tables fairly stout, basal 

 part usually conical with a few spines and the top carrying two sets of 

 spines, forming a double Maltese cross; often small spines intercalated 

 between the typical eight pairs, especially in the few tables with the 

 disk still preserved. A scattered deeper layer of flat rods or bars, with 

 marginal holes or dentate edge. Ventral feet with large end plate and 

 large supporting plates with lateral holes ; dorsal appendages with small 

 end plate or none and shorter, usually curved, rods, often with dentate 

 ends. 



Color usually dull grayish brown with slightly paler area around 

 the appendages and a varying number of dark dots, sometimes fused to 

 two rows of dark spots on the dorsum; ventral side usually paler. 



Type: In Germany; paratypes in the Museum of Comparative 

 Zoology. 



Type locality: Panama. 



Distribution: Apparently restricted to the waters around Panama 

 and a few localities along the coast of Mexico, including Cape San 

 Lucas. 



Specirnens examined: Selenka's co-types and sixteen specimens 

 secured by the Hancock expeditions in Panama, Bahia Honda, and Ta- 

 boga Island; Mexico, Tenacatita Bay, Las Tres Marias, Los Frailes, 

 and Cape San Lucas. All ranging from 4 to 10 cm in length and mostly 

 dull grayish brown in color. 



Remarks: Selenka's description and figures, though far from per- 

 fect, leave no doubt as to which species he had before him. He figured 

 the characteristic spinous conical base of the table and attempted to 

 figure the top with its two circles of spines. Among the large rods, he 

 unfortunately selected one with lateral teeth not united into marginal 

 holes. His types have been re-examined and it was discovered that two 

 of his seven specimens were Semperothuria languens, one was a con- 

 tracted specimen of Selenkothuria portovallartensis, and four were 

 Semperothuria imitans. This explains why Deichmann in 1930 was mis- 

 led into thinking that Selenka's species was characterized by tables with 

 a single circle of spines (as in 5. imitans). 



The species is obviously closely related to Semperothuria surinamen- 

 sis, the common species in the West Indies, and Semper's reference to 

 "H. languens'^ in that region refers undoubtedly to that species. The 

 rather restricted distribution of Semperothuria languens seems to indi- 

 cate that it is derived from West Indian stock, while the more common 

 form, S. imitans, has come from the West Pacific. 



