FAUNA OF LIGNITES. 167 



Of the lower animals Prof. Heer only knows a few species of 

 Mollusca and insects. The former occur by thousands in the 

 clays. Besides fragments of Anodonta, only three species can 

 be recognized, namely Pisidium obliguum, Lam., Valvata obtusa, 

 Drap., and a variety of V. depressa, Pfeif. These are animals 

 that still occur in the same district ; the Valvata live in the 

 brooks traversing the peat-bogs. 



Insects are found partly in the lignite and partly in the clays. 

 The former are almost exclusively species of Donacia ; but these 

 occur in such quantities that their elytra lie by hundreds in 

 some parts of the lignite ; they still retain their metallic blue and 

 green colours, and form brilliant coloured specks on the black 

 ground. The elytra are most frequently met with ; the thorax 

 and legs are less common, and the latter are generally separated 

 from the body. No doubt these beetles lived on the aquatic 

 and marsh plants of the turbaries. At their death they fell 

 into the water and became broken up; and only the harder parts 

 (especially the elytra) sank to the bottom with other organic 

 matters, and thus got imbedded in the peat. When fresh from 

 the pit they are admirably preserved ; but as the lignite shrinks 

 in drying, they are either destroyed by this process or so twisted 

 and distorted that they are no longer fit for investigation. By 

 the form and configuration of the elytra, two species may be 

 distinguished at Diirnten and Utznach ; these are identical with 

 species now living about the Swiss lakes and marshes (Donacia 

 discolor, Gyll., and sericea, Linn.) . The most abundant species 

 is Donacia. discolor, which was adorned with green and blue 

 metallic tints, and agreed perfectly with the existing form in the 

 configuration of the elytra, the fine transverse wrinkling, the 

 punctate striae and the mode of their union (fig. 353), and the 

 uniformly and densely punctate prothorax (fig. 355). In the 

 male (fig. 354) the posterior femora were also much thickened. 

 The nearly allied Donacia sericea, Linn. (fig. 352) is less abun- 

 dant ; in this species the punctate striae are less distinctly marked 

 at the apex of the elytra, where they become confounded with 

 the other 'punctures of that part. The larvae of these two spe- 

 cies, and their nourishment, are still unknown; in the adult 

 state they are found all over Europe, even as far as Lapland, on 

 reeds and sedges. 



