Genus— 0 NYCHOPRION. 
Onychoprion Wagler, Isis 1832, p. 277 Type 0. fuscatus, 
Planetis Wagler, Isis 1832, p. 1,222 . . . . . . Type 0. fuscatus. 
{Also spelt Planetes Gistel, Naturg. Thier. Schul., 
p. X., 1848.) 
Haliplana Wagler, Isis 1832, p. 1,224 . . . . . . Type 0. fuscatus. 
Thalassipora Riippell, Syst. Uebers. Vogel Nord-ost-Afr., 
p. 140, 1845 . . . . . . . . . . . . Type 0. fuscatus. 
Dipsaleon Gistel, Naturg. Thier. Schul., p. x., 1848 . . Type 0. fuscatus. 
(New name for “ Planetes Wagl.”) 
Medium sized Terns with comparatively short stout bills, short legs, long 
wings and very long tails. The culmen is a little longer than the head, and 
much longer than the tarsus. The nature of the nostrils shows an approach 
to that seen in the Noddies. The toes are comparatively short and fully 
webbed. The streamers are well developed, making the tail more than half 
the length of the wing. 
Most writers upon the Terns have intimated their disapproval of lump- 
ing this species in with Sterna, but have all been unable to find distinct 
structural differences in the skin to justify the separation. The nature of the 
young has influenced me in accepting Onychoprion, while most writers have 
commented upon its habit of laying one egg only. 
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