BUFFALO SOCIETY OF NATURAL SCIENCES 137 



textbooks and by authors generally. The main statement that is 

 dwelt upon insistently, and which is so dangerously plausible, is that 

 in the Wenlock the eurypterids are found in an undoubted marine 

 formation in association with typical marine fossils. Such a state- 

 ment is full not of truths, but of half truths, and these are far harder 

 to combat than actual untruths. In the present instance we have 

 only to consider how much weight would attach to such a statement 

 if the following significant bits of information were added: (1) The 

 eurypterids do not occur in the same beds with the undoubted marine 

 forms, but always in certain leaf -thin bands which carry no other 

 fossils except Dictyocaris ramsayi, a form which may be a fluviatile 

 if not a terrestrial plant or animal, but the systematic position of 

 which is at present wholly undetermined. The thickness of all the 

 beds containing the eurypterid-bearing bands is only one foot; it is 

 a grit and greywacke; the typical marine fossils are found in the 

 shales and in limestone lenses. (2) Not a single complete euryp- 

 terid has been found among the hundreds of specimens collected and 

 the very species described by Laurie have usually been founded upon 

 fragments. (3) The exoskeletons have not only been dismembered — 

 this might be expected in any case, for tluring the process of decay 

 the various members might fall apart and thus be embedded in the 

 mud, few complete individuals being entombed — but the fragments 

 are macerated, the edges are broken and worn, the surface sculp- 

 turing indistinct, altogether showing evident signs of wear. (4) The 

 occurrences are not widespread; although many good sections are 

 obtainable in the Pentland Hills inlier, in only two places are euryp- 

 terids found. In both cases the remains are confined to bands a 

 few inches thick, extending laterally but a few feet. (5) The euryp- 

 terid fauna appears suddenly with no forerunners and no descendants 

 so far as may be judged from the faunas of the beds immediately 

 below and above the bands containing eurypterids; two of the five 

 genera are confined to this horizon. (The full significance of state- 

 ments (4) and (5) will be taken up in the next chapter on distribution.) 

 These are the facts which are generally not mentioned when the 

 eurypterids are declared to be abundantly represented and associated 

 with a good marine fauna. These five facts seem to be difficult of 

 explanation if it be supposed that the eurypterids were marine organ- 

 isms. How are we to account for the fact that the merostomes 

 accompanied by that form which so often occurs with them, Dictyo- 

 caris ramsayi, are found in layers separated from those containing 



