Mr. Kirby on the Tarsus of Coleoptera. 195 



on the supijosition, either of a subsidence of the ocean below 

 its original level, or a heaving up of the island by a force from 

 beneath. If we admit the former of these causes, indications 

 of a similar subsidence ought to be found on the adjacent 

 coasts : but I am not aware of any such having been observed. 

 The great inclination of the strata, and the dislocation they 

 sometimes appear to have suffered, would seem to favour the 

 latter hypothesis. It must still however be regarded as a phse- 

 nomenon of a most singular kind, that so large an island, di- 

 versified with numerous hills from 800 to 3000 feet in height, 

 should have been heaved up from the sea with so litde dis- 

 turbance to the fragile marine productions on the surface. 



The appearance and nature of these productions would in- 

 dicate a comparatively recent date to the event. 



The other large islands of the chain, Pulo Batu, Mantawi, 

 and the Poggies, are less known, but are probably not very' 

 dissimilar in structure to Pulo Nias: they are not nearly so- 

 populous or so well cultivated ; but the quantity of sago and 

 cocoa-nuts which they produce sufficiently proves that they 

 j.re not deficient in fertility and natural resources. 



The islands on the eastern side of Sumatra are of two de- 

 scriptions : those which lie off the mouths of the Siak and In- 

 dragiri rivers, on the western side of the Straits of Malacca, 

 are merely alluvial flats; while the islands of Banca, Lingen, 

 &c., may more properly be considered as belonging to the 

 Malayan chain, and as a continuation of the I'ange which forms , 

 the peninsula of Malacca, being similar to it- in geological 

 situation, and in their mineral products, the most abundant 

 and remarkable of which is tin*. 



XXXI. On the Structure of the Tarsus in the Tetramerous and 

 Trimermis Coleoptera of the French Entoinologists. By the' 

 Rev. W. Kirby, M.A. F.R.S. 4' L.S. ^c. 

 To the Editor q/'the Philosophical Magazine and Journal. 

 Deaf sir, 



EpROM the abstract you have given in your last Number, of 

 •*■ a paper of my friend Mr. W. S. MacLeay's, On the struc- 

 ture of the tarsus in the tetramerous and trimerous Coleoptera of' 

 the French entomologists, read at the Linnaean Society, it appears 

 that he was not aware of its having been long ago discovered 



• In the collection of rocks sent by Dr. Jack from Sumatra occurs a 

 speciriicri, No. 1!),.'{4.J, of soft white chalk, Cicttt scriptoria, containing the 

 fraKinLiit<)f an echinus. No mention of it is made in the memoir, nor 

 «as any infornnition contained in the label attached to it, except the loca- 

 lity, Hencoolen. — N«tr hi/ the Sfcrtlmirs. 



Vol. 6.5. No. 323. JV/a/r/j IH'^.n. Bb by 



