336 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



The 3 species discussed' below are separable as follows. 

 1. Paleae of outer opercular series with strongly curved, plumelike 

 shaft (pi. 31, fig. 35) I. pennatus 



1. Paleae of outer opercular series with nearly straight shaft . . 2 



2. Spinelets on outer paleae widely separated, curved outward (pi. 

 31, fig. 36) /. armata 



2. Spinelets on outer paleae closely spaced, appressed to shaft (pi. 

 31, fig. 34) /. ornamentatus 



Idanthyrsus pennatus (Peters) 

 PlateSl, Fig. 35 



Fauvel, 1917, pp. 262-264 (with synonymy). 

 /. cretus Chamberlin, 1919, pp. 485-487, pi. 75, figs. 8-15. 

 /. regalis Chamberlin, 1919, pp. 487-490, pi. 74, figs. 1-8. 

 Johansson, 1927, pp. 88-90. 



Collections. — (Most are tube masses, the number of individuals is 

 therefore not stated save in a few instances.) 30-33 ; 56-33 ; 69-33 ; 80-33 ; 

 94-33; lOla-33; 129-33; 239-34; 258-34; 261-34; 413-34; 414-45; 433- 

 35 ; 435-35 ; 444-35 ; 447-35 ; 464-35 ; 859-38. 



Other material examined. — At the U.S. National Museum, type of 

 /. cretus, from Taboguilla Island; type of /. regalis , from Chatham 

 Island, Galapagos, shore; specimens from Punta Santa Elena, Guayaquil, 

 Ecuador, tide pool, several tubes collected by W. L. Schmitt. 



The type specimen of /. cretus Chamberlin (USNM no. 19716) is 

 so fixed that the operculum is expanded, hence described as "opercular 

 lobes . . . diverging." Though much smaller than the type of /. regalis 

 Chamberlin (USNM no. 19385), it agrees well in all details, and both 

 must be referred to the older /. pennatus (Peters). They were originally 

 considered distinct because of differences in comparative sizes of the 

 dorsal thoracic paleae, a difference which is believed to be due to varying 

 sizes of the entire body. Johansson (1927, pp. 88, 90) has already con- 

 sidered them with /. pennatus. 



Distribution. — /. pennatus was originally described from Mossam- 

 bique, but has been widely reported from tropical parts of the Pacific 

 and Indian oceans; in the Western Hemisphere it occurs from western 

 Mexico, south to Ecuador, from shore to 18 fms. 



Idanthyrsus armatus Kinberg 

 Plate 31, Fig. 36 

 Kinberg, 1867, p. 350. 



Hermella macropalea Schmarda, 1861, pp. 23-24, pi. 20, fig. 172 (in 



part). 



