64 Prof. Hitchcock on Fossil Footmarks, Lincohiite, 6^c. 



somewhat larger, (and I incline to the opinion, that some of them 

 are really from eighteen to twenty inches long,) yet I preferred 

 to give one, about which there could be no doubt ; and I choose 

 to have it fall short of, rather than exceed, the truth. Allow me 

 to add, that the track figured in your Journal, was the first one I 

 ever discovered of this giant species; and I well recollect how I 

 was on the point of rejecting it, because it seemed impossible 

 that it could be a real track. I ought not, therefore, to be sur- 

 prised at the great scepticism manifested by so many, who had 

 only a drawing to look at. 



There is another circumstance that would make the track of 

 the same bird longer or shorter, according to the depth to which 

 its foot sunk in the mud. I have never seen a specimen of this 

 species, in which a distinct impression of the distal extremity of 

 the tarso-metatarsal bone exists. But the cushion beneath the 

 distal end of the proximal phalanges, sloped backwards in such 

 a way, that the deeper the foot sunk, the longer would be the 

 track. In the specimen figured in your Journal, the depth of the 

 impression was not very great ; so that perhaps the very next 

 step might have been somewhat longer. 



But to turn to another subject. I feel really in doubt whether 

 to say any thing farther about the Lincolnite, since the mineral 

 is so small, and so rare, as hardly to be worth any farther discus- 

 sion. Allow me, however, to express the belief, that your note, 

 appended to my statement in the last number of the Journal, 

 does not settle the question ; as I think I could satisfy you, were 

 it in my power to send you specimens. For the modifying plane, 

 which you suppose Prof. Shepard has mistaken for a primary 

 plane, I have never noticed, except in two or three instances; 

 and then it was so very narrow, (much more so than the figure 

 in my Final Report,) as to be visible only by a good glass; and 

 it could not, therefore, have been confounded with the primary 

 planes, by so practised an observer as that gentleman.* I shall 

 be surprised if he does not confirm this statement. Nearly all 



* The plane e (/in Phillips's figure) enlarged, may obliterate M, one of the lat- 

 eral primary faces, or reduce it to a narrow plane, resembling the e in common crys- 

 tals of Heulandite; in this case the crystal would still be a right-oblique angled 

 (right rhomboidal) prism, with M (if present) a narrow plane replacing a lateral 

 edge. This narrow plane we have supposed to be the one above alluded to in the 

 crystals of Lincolnite. — Eds. 



