326 Rev. F. D. Morice's Notes on Australian Sawfiies. 



in $$ (not $<$) of the latter group. Nine, instead of being 

 the normal number of their joints, is about the rarest of 

 all : almost confined to one genus, Eurys, and even there 

 by no means universal, while the form of the joints is never 

 simply cylindrical. 



The most characteristic of the Neogaeic Genera resemble 

 one or other of the Australian groups in their antennal 

 characters. But genera also occur there which seem to 

 have arrived more recently, either identical with present 

 Arctogaeic groups or very closely related to them, and in 

 these the antennae are of the prevailing Arctogaeic Type. 



(d) Mouth- part*. The palpi. — Having examined dissec- 

 tions of the mouth-parts in many Arctogaeic Tenthreilinidae 

 I have invariably found that the maxillary palpi had 

 6 joints and the labial 4. The same numbers are normal in 

 other Hymenopterous groups, though there are exceptions, 

 e. g. the Bees. 



But this rule is by no means so universal either in 

 Notogaea or Neogaea. Citing only cases where I have 

 myself examined the dissections, I can testify that in the 

 Australian genera Phylacteophaga, Philomastix and Perga 

 — not, however, in Xyloperga — and in the Neogaeic Incalia 

 (hirticornis), Pachylosticta (= Plagiocera) albiventris, and 

 Lophyroides (— Perreyia, Auctt. nec\ Brulle) tropicus 

 the numbers of joints are not 6 and 4 respectively, but 

 4 and 3. Again in Syzygonia they are 5 and 3, and in what 

 I take to be the real Perreyia, Brulle, actually only 2 (or 

 possibly 3) and 1. 



There is no doubt that two or more quite unrelated 

 groups might independently undergo a similar modifica- 

 tion of their mouth-parts, and again that groups very 

 nearly related might differ in this character, through 

 adaptation to some special circumstance connected with 

 their feeding. (Mr. Turner has thus explained a difference 

 in the development of their palpi between the American 

 and Australian Thynnidae.) 



But it seems highly improbable that the agreement in 

 so unusual a character between certain particular groups 

 in two very distant districts, these groups having also a 

 singular affinity in other quite dilTerent characters, should 

 be a mere coincidence, the American and Australian forms 

 having (as Cameron suggests) developed the reduction in 

 the number of these joints independently since they 

 reached their present habitats. I should suspect rather 



