326 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 11 



will be found to be identical with one of the older forms and thus repre- 

 sent a migrant from the Indo-Pacific. 



No attempt has been made to compose a key, as I feel I have not 

 enough material from the Indo-West Pacific to justify it. The other 

 species which in my opinion should be referred to the genus are: Theel- 

 othuria squamata (Semper), T. spinulosa (Theel), and T. maculosa 

 (Pearson), all placed in the same group as T. princeps in Panning's re- 

 vision; Ludwig's T. notabilis (and Deichmann's Holothuria imperator), 

 referred to another group; and Semper's Theelothuria aculeata, which 

 Panning places in a third group — an indication of how difficult it is to 

 interpret the older descriptions without any material. But even where 

 material is available, it is not too easy to draw the line between these 

 forms. 



Theelothuria paraprinceps (Deichmann) 

 PI. 9, figs. 1-18 



Holothuria paraprinceps Deichmann, 1937, p. 166, text-fig. 1, nos. 1-10. 

 Steinbeck & Ricketts, 1945, p. 409, pi. 19, fig. 1. 



Diagnosis: As for the genus, with the buttons in older individuals 

 becoming smooth, fairly regular with minute holes or none, particularly 

 in the ventrum. Color varying from almost black with a narrow light 

 ring around the base of the appendages to light brown with two rows of 

 darker spots on the dorsum and also in some cases a darker area along the 

 middle of the ventrum. The general impression of the light-colored indi- 

 viduals is of mixed salt and pepper. Young individuals, few cm long, 

 almost colorless, the slightly larger ones reddish brown, often with the 

 appendages pale except for a ring of dark pigment near the base, setting 

 off the light area around it. 



Type: Museum of Comparative Zoology. 



Type locality: Arena Bank, Gulf of California, 35 fathoms. 



Distribution: As far as known ranging from the lower end of the 

 Gulf of California to Panama (material in Copenhagen) and southward 

 to Cocos Island, also taken at Clarion Island. 



Depth: From tidemark down to about 35 fathoms. 



Specimens examined: The type, several specimens collected by 

 Steinbeck & Ricketts (all dark) from El Mogote, Lower California, one 

 collected in Panama by Dr. Mortensen, and eight specimens collected by 

 the Hancock expeditions, from Cocos Island, 30-50 fathoms. Clarion 

 Island, shore and 28-35 fathoms, and from Cape San Lucas and Concep- 

 cion Bay (26° N). 



