DISTRIBUTE INSECT VARIETY. 265 



Sphinx moths [Lejridojdera heterocera) now poise in the twilight, 

 appropriate food for the bat-like pterodaetyles. 



During these ages of the Jurassic Sea, when coral reefs 

 fringed the coast-line of Professor Heer's"^ Gulf of Alsace, 

 there reigned not yet over Palsearctic and Neartic areas that 

 death-like stillness of summer so felt by the tropical traveller. 

 For from the earliest days of the Devonian flora, the shrill of 

 arboreal crickets echoed in the coverts of our atolls, and now 

 again we catch from bush and dell the dream-inviting dirl of 

 huge and voracious Dectici at autumn, while the vernal ground 

 echoed to the " erink-crink " of Grylli, near akin to the present 

 field and wood cricket, or the woodland hush was broken by the 

 startling calls and whirr of large cicada? {Homopterd) . This 

 quasi-tropical harmony presented by our island eastward, emerg- 

 ing from the Jurassic waves, is further attested in the character 

 of its wood-destroying beetles, the Longhorns, Weevils, and 

 Bupresticke, the great size of its Dragon-flies and Leaf-crickets, 

 or we may note it in the Cycads and Zamias that abounded 

 among the coniferous forest. The stems of the latter in the 

 Isle of Portland and on the denuded face of a cliff at Lul worth 

 Cove were found, together with these carboniferous trees, 

 actually rooted in the " dirt bed " or soil in which they grew, 

 still exhibiting their petrified buds and at least evidence of their 

 plumy foliage. This palmy thicket is covered over successively 

 by the deposits of a lake and estuary, capped by the organic sea 

 muds accruing from the continued land depression and conse- 

 quent westward reflux of the cold cretaceous ocean, which as the 

 land sank and shore line receded, threw down its clays and green 

 sand, the spoil of ground swell and tides, and over these white 

 chalk and lines of black flints, the long slimy accumulation of 

 deeper sea microcosms, the round Foraminifera shells and flaky 

 vegetable Diatomaceae. 



In the Cretaceous period, according to Prof. DaAvson, the great 

 continental plateaus were brought down, for the first time since the 

 early Laurentian, to the condition of abysmal depths. This 

 depression affected Europe moi'e severely than America, the 

 depression of the latter being not only less but somewhat later in 



* Professor Heer, " Primasval World of Switzerland." 



