Palcoiitological Speculations.— Grafacap. 89 
Scolithus is prevalent in Potsdam layers, the chloritic slates 
of the Kenebec river, Maine, are thickly covered with the trails 
of worms (Chaetopods?), Arenicolites, as determined by Whit- 
field, fills broad spaces of the Barriboo beds in Wisconsin. Nath- 
orst has indicated the numerous traces of annelidan tracks in 
Scandinavian Cambrian. Climactichnites and Protichnites 
may all be the reptant impression of large broad ringed worms. 
It seems impossible to reject the patent suggestions of bi- 
ology which are thus partially reinforced by the indeterminate 
but significant instances of fossil traces. 
In considering further the hypothetical picture of primor- 
dial zoic tendencies the condition seems obvious that in shallow 
water forms — the trilobites and ecardines — we have chitinous 
integuments, in the deep water calcareous, mainly presented. 
This seems connected with initial histological peculiarities 
which no refinement of chemical biology can yet completely 
touch. The contrasting and separative features between a 
shore and a deep-water existence are of course primarily the 
longer exposure to light, and greater likelihood of mechanical 
violence, on the later removal from these vicissitudes and sub- 
jection to pressure with a richer supply of dissolved mineral 
materials. 
Simroth in his interesting section "Einfluss der Atmosphare 
auf das Integument," has offered some instructive parallelisms, 
symptomatic, in the case of the shore animals, of the stages in 
their assumption of hard coverings. The hardening of the 
epidermis by exposure to air and light led he thinks to the 
gradual replacement of the hairy surfaces of the worms by 
soft chitinous coats, which grew stronger and thicker as the 
metamorphosis went on and the changes to such a triplicate 
exoskeleton, as the arthropods possess, were completed. 
The Brachiopoda have been clearly considered referable 
to the annelids. Prof. Sedgwick believes "we must assign to 
the group the position of an independent phylum of the animal 
kingdom with affinities, by the form of their central nervous 
system and by their setae, by the presence of a well-developed 
perivisceral coelom and a canalicular haemocoel, and by the 
traces of an imperfect segmentation, to the Annelida." We 
find therefore the phosphatic thin shelled atrematous Brach- 
iopoda and the chitinous covered trilobites well represented 
