ELISHA MlTCHEI^Iv SCIENTIFIC SOCIETY. 59 



g-eometric figure and its freedom from rigidit}^ in its 

 appearance, either in form or marking's, sug^crests that 

 it is not of inorg-anic orig-'in. And 3'et the persistence 

 in conforming- to a g'eneral outline, in the radial g-roov- 

 ing-s, and the rounded knob at one apex with the 

 smooth cavit}' at the other makes the conclusion irre- 

 sistable that it is not "accidental, " that they were all 

 formed under like conditions and in accordance with 

 certain laws, and no mode of crystrdlization or wholly 

 inorg-anic arrang-ement can be conceived that will sup- 

 pi}^ the conditions or sug-g'est the laws capable of imi- 

 tating* these forms. The rounded knob and the cavit}^ 

 opposite are ver}^ striking-. I have examined many 

 isolated specimens and without exception the knob and 

 cavit}^ are present. Those exposed on the surface of 

 the rock, as has been pointed out, g-enerally show one 

 of the apices, and of those I have examined — upwards 

 of 300 in all — not one failed to present either a knob or 

 a cavity,^ with the exception of not more than four 

 whose apices had been so crushed by pressure that 

 these characters had been destroyed, or the knob sim- 

 ply broken off as in fig-ure 11. I have never 3-et found 

 one that had a knob at each apex or a cavit}^ at each 

 apex. These two marking-s seem to be as persistent 

 and as characteristic as the two valves of a brachiopod. 

 The cavity has the exact appearance of the socket 

 of a ball and socket joint. The inner surface appears 

 perfectly smooth under a magnifying- glass and viv- 

 idly suggests that it has been the seat of an organ or 

 of an organism. 



(3) It has been shown so far that the palaiotrochis 



1. This statement applies only to these which present an apex and 

 not to tho::e rare exceptions that do not present either apex. 



