386 Mr. G. H. K. Thwaites on Lichens. 



Polyachus hicolor. 



P. oblongo-ovatus, convexus, niger, nitidus, capite, thorace pedi- 

 busque rufo-testaceis, antennis fulvis, extrorsum nigris ; thorace 

 remote punctato ; elytris sat fortiter punctato-striatis, interspatiis 

 planis, duobus extemis convexiuseulis. 



Long. I lin. 



Hah. Gawler Town, South Australia. 



Vertex smooth, impunctate ; clypeus semiovate, impressed 

 ■with a few remote punctui-es ; eyes large, subangulate-emar- 

 ginate, moderately distant, black ; antenna with the six upper 

 joints slightly thickened, the four outer ones black. Thorax 

 about twice as broad as long ; sides rounded and converging 

 from base to apex ; basal margin slightly bisinuate on either 

 side ; median lobe produced, angulate, its apex rounded, entire ; 

 upper sui-face transversely convex ; subcylindrical at the apex ; 

 apical and basal margins each bordered with a single row of 

 punctures, disk remotely punctured ; extreme basal margin 

 narrowly edged with piceous. Scutellum narrowly oblong, 

 its apex obtuse. Elytra strongly punctate-striate ; interspaces 

 smooth, impunctate, two outer ones slightly convex. 



Very similar in form and coloration to Bucharis mar tins ; 

 in addition, however, to the structural difference in the antenna, 

 it may be at once known by the different form of the basal lobe 

 of the thorax : in B. martins it is thickened, its apex being 

 acuminate ; in the present insect the lobe is flattened, forming 

 a thin plate, and its apex is rounded. 



[To be continued.] 



XLIX. — Note on Lichens. 

 By G. H. K. Thwaites, F.R.S. 



My thoughts have been much occupied of late upon the sub- 

 ject of lichens and their development, and especially with 

 reference to the views of Schwendener and Bornet, and of 

 some other botanists who coincide with them in advocating 

 the theoiy oi parasitism as explanatory of the structural com- 

 position of lichens. 



I have not the least desire, nor have I any intention to 

 impugn tlie correctness of the descriptions and of the beautiful 

 delineations of Mons. Bornet (^ Annales des Sciences Natu- 

 relles,' 4^ sdrie, tome xvii.) ; but I must candidly confess that, 

 after prolonged consideration, I cannot bring myself to yield 



