Genus— T HALASSARCHE. 
Thalassarche Reichenbach, Nat. Syst.Vog., p. v., 1852 Type Th. melanophris. 
(Also spelt Thalassiarche.) 
When Reichenbach generically separated the Albatroses, he introduced 
Thalassarche for the birds ranged about D. melanophris. We do not know 
the limits of his genus nor his generic characters, so we are left to guess that 
he would have included all the MoUymawks under that name. Coues lumped 
these as “ Group B,” and wrote : “ Melanophrys may be taken as the type 
of this group, which constitutes the genus Thalassarche Reich.” Forbes con- 
sidered Thalassarche a good genus. Ridgway, concluding that the type of 
Thalassarche was a typical Diomedea, introduced Thalassogeron for the Molly- 
mawks with D. culminata Gould as type. By some authors Thalassarche 
(written Thalassiarche Forbes) has been considered equivalent to Thalassogeron 
Ridgway, but I would point out that Forbes’s two species of Thalassarche were 
Th. melanophris and Th. culminata^ so that his genus was more probably the 
same as Reichenbach’s. 
More recently Thalassarche has been considered synonymous with Diomedea, 
while Thalassogeron has been admitted as a valid genus. Careful examination 
of the bills of Diomedea melanophris and the other MoUymawks proves that 
they must be classed together. Essentially they agree in having the bill 
shorter and weaker than in D. exulans, and in having the nostrils small and placed 
at some distance from the base of the biU and not as in D. exulans. There can 
be no good reason for placing D. melanophris in Diomedea if Thalassogeron be 
retained. And unless Thalassarche be used for the MoUymawks as a whole, 
and Thalassogeron rejected, both must be utilised. In the American Ornith- 
ologists’ Union Checklist subgenera are freely accepted, and the value of Thalas- 
sogeron would seem to be only subgeneric to Thalassarche. Thus the culmen 
of Th. culminatus is cleanly separated, posterior to the nostrils, from the 
latericorn by a Ueshy membrane ; the cuTmen however reaches right up to the 
feathers of the forehead. In D. melanophris the culmen, posterior to the 
nostrils, broadens and spreads downwards to the latericorn, from which it is 
264 
