Scientific Intelligence. — Zoology. 379 



thought, was the movement which attracted most observation, giving 

 rise as it does, to sudden and abrupt changes of relation on the sur- 

 face of the earth, at places where the formation of the strata admits 

 of more or less freedom of movement, causing the sudden shocks 

 which are so destructive. 



Professor Rogers is of opinion, that the thickness of the earth's 

 crust, in most places, is not more than ten miles. — {American 

 Journal of Science and Art, vol. xvii., p. 135.) 



27. Coloration. — Coloration cannot be made use of as a generic 

 character, and its importance to the palaeontologist is small, but when 

 occurring on fossil forms it should always be noted. Professor Forbes 

 has kindly informed me, " that his observations on the distribution 

 in depth of recent species, have led him to the conclusion, that definite 

 patterns, i.e., stripes, bands, and waves of colour, vividly marked, 

 do not occur, except in rare instances, on shells living beyond mode- 

 rate depths, as below fifty fathoms or thereabouts ; and that thus we 

 may be enabled to come to approximate conclusions respecting depths 

 of ancient seas from the patterns preserved to us on fossil shells." 

 The coloration is of some use in distinguishing the recent terms of 

 Brachiopoda ; green, yellow, red, and bluish-black, being the prevail- 

 ing colours : several forms are striped or spotted with red. Among 

 the fossil species, some examples have preserved traces of their colours, 

 as already mentioned in Part iii., p. 6, and several other examples 

 will be hereafter noticed so that in all probability the species now 

 extinct, when alive, presented all the rich varieties of tint, observ- 

 able in the present inhabitants of our seas. — [British Fossil Brachi- 

 opoda, vol. i., p. 53.) 



ZOOLOGY. 



28. Observations on the Habits of certain Craw-fishes. — (In a 

 letter of Dr R. P. Stephens to the Smithsonian Institution.) " Our 

 friends the Astaci increase in interest as I become more and more 

 acquainted with their habits and instincts. I have learned this month 

 that they are migratory, and in their travels are capable of doing 

 much damage to dams and embankments. On the Little Genesee, 

 they have, within a few years, compelled the owners of a dam to re- 

 build it. The former dam was built after the manner of dikes, i.e., 

 with upright posts, supporting sleepers laid inclining at an angle of 

 4.5° up the stream. On these were laid planks, and the planks covered 

 with dirt. The Astacus proceeding up stream, would burrow under 

 the planks where they rested on the bottom of the stream, removing 

 bushels of dirt and gravel in the course of a night. I have seen this 

 season, where they had attempted the present dam, piles of dirt, of 

 at least one bushel. 



" They now travel over the dam in their migrations, often climbing 

 upright posts, two or three feet high, to gain the pond above." — 

 (American Journal of Science and Arts, vol. xvii., p. 134.) 



29. Arctic Whale fisheries. — The extraordinary success which has 



