288 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 11 



from Thursday Island, appears to be young individuals of Mertensio- 

 thuria leucospilota (Brandt). The remaining six species are reduced to 

 three: Microthele difficilis (Semper), including Holothuria excellens 

 (Ludwig), H. bedfordi (Deichmann), and H. altimensis H. L. Clark; 

 Microthele sanctori (delle Chiaje), with its synonym Holothuria flavo- 

 castanea (Theel) ; and Microthele parvula (Selenka). 



Key to the species of the genus Microthele 

 Brandt, emend. Panning 



1. Large species, 20 cm, brown with paler area around the dorsal 

 papillae. Mediterranean, Eastern Atlantic, as far south as St. 

 Helena sanctori (delle Chiaje) 



1. Small to medium-sized species. Color uniformly brown or yel- 

 low 2 



2. Specimens about 5 cm long, color light brown or yellow. But- 

 tons comparatively narrow, often S-shaped. West Indies, in- 

 cluding Bermuda parvula (Selenka) 



2. Specimens up to 10 to 12 cm long; color usually dark brown. 

 Buttons broad oval. Indo-Pacific. . . . difficilis (Semper) 



Microthele difficilis (Semper) 

 PL 1, figs. 6-9 



Holothuria difficilis Semper, 1868, p. 92, pi. 30, fig. 21. Panning, 1929, 



I, p. 136, text-fig. 20 (copied from various authors), complete 



list of references. Deichmann, 1937, p. 164. Steinbeck & 



Ricketts, 1941, p. 407. 

 Miilleria excellens Ludwig, 1875, p. 98, pi. 7, fig. 32. 

 Holothuria (Microthele) excellens, Panning, 1929, I, p. 132, text-fig. 



16 (copied from Ludwig). 

 Actinopyga bedfordi Deichmann, 1922, p. 212. 

 Holothuria (Microthele) bedfordi, Panning, 1929, I, p. 136, text-fig. 



19 (copied from Bedford). 

 Holothuria frequentiamensis H. L. Clark, 1902, p. 530. Panning, 1934, 



III, p. 73. 

 Holothuria altimensis, H. L. Clark, 1921, p. 172, pi. 37, figs. 20-29. 



Panning, 1935, IV, p. 94, text-fig. 82 (copied from H. L. 



Clark). 

 Diagnosis: Medium-sized form, 10 to 12 cm long, usually dark 

 brown, sometimes almost purplish black, rarely more yellow. Spicules a 



