594 REVISIONAL NOTES ON AUSTRALIAN CARABID-E, V., 



ly striate ; interstices punctate ; apex truncate, membranous. 

 Anterior tibiae elongate, narrow, inner notch towards distal 

 end ; tarsi setose, fourth joint entire, in cf second and third 

 joints lightly dilatate, and biseriately squamulose beneath. 

 Habits either terrestrial, or on tree-trunks, under bark. 



Gigadema represents the central stem of the Australian 

 Belluonides, with affinities in different directions towards 

 Hellua'pterus, Helluarchus, Amefroglossus, Neohelluo, and 

 j^nigma. Its most puzzling species is G. longipenne, which, 

 though evidently a true Gigadema, resembles Helluo in the 

 form of its mentum, ligula, and maxillae. 



Variations. — Aiitennw. length and setosity of four basal 

 joints (compare G. sulcatum and G. hostocki). Mentum: 

 median tooth prominent and excised at apex (e.g., G. nocte), 

 short with apex rotundate (e.g., G. rugaticolle) . Ligula: 

 convex and non -setose {G. lo?igipenjie), or more or less de- 

 pressed and setose; paraglossae membranous (G. sulcatum), 

 corneous [G. hostocki). Maxillce: form of inner side, of apex; 

 set of hook ; setosity (compare G. maxillare, G. longifenne, 

 and G. hostocki). Palpi: length, especially of penultimate 

 joints (compare G. sulcatum and G. hostocki). Prothorax: 

 form and puncturation. Elytra: interstices pluripunctate 

 (G. maxillare), biseriate-punctate ((7. 6os/.oc/:i). Trochanters: 

 posterior oval or pointed (only G. grande) ; intermediate tri- 

 angularly prominent in middle {G . longipenne). 



Secondary sexual characters of cf '• mandibles very long 

 and decussate {G. grande var. prominens) ; right mandible 

 notched towards apex {G. hostocki). Suhmentum armed (in 

 G grande -groM^). Maxillae with cardo armed {G. maxillare). 



Phylogeny. — The sulcatum-gr om^ is the most ancient by 

 short joints of palpi ; strong tooth of mentum ; membranous 

 paraglossae with apex free ; closely punctate disc of prothorax ; 

 setose inflexed margins of elytra, etc. The grande-gron-p must 

 also be placed below the 7iocte-gYouip by form of palpi ; form 

 of ligula, including membranous paraglossae ; the nocte-grouY) 

 is the most recent. G. longipenne may have diverged from the 



