Association of American Geologists and Naturalists. 249 



this stage of research, my brother was fortunate enough, about two 

 years ago, to discover in the formation in Virginia, two or three small 

 shells, and to recognize, in the most abundant of these species, the Po- 

 sidonia Keuperi, a well known and characteristic species of the Trias, 

 or upper new red sandstone of Europe. With this positive link, sup- 

 ported by the strong analogies already mentioned, the most skeptical 

 can no longer hesitate to refer our red sandstone formation to some part 

 of the Triassic or earliest mesozoic period. The conjecture recently 

 expressed by Mr. Murchison, therefore, that the Connecticut deposit is 

 of the age of the magnesian limestone group, or the Permian system of 

 this able geologist, resting as it does chiefly on the occurrence of the 

 genus Palseoniscus, but not on an identity of species, cannot be consid- 

 ered as consistent with the other more conclusive evidence which we 

 now possess of a difference of date ; and should it hereafter appear, as 

 seems to be suspected by Mr. Redfield, that the American fishes referred 

 to Palseoniscus, constitute truly a new though allied genus, even the 

 present supposed generic relationships of the formations will vanish. 

 The fact mentioned by Mr. Redfield, that " the scales and apparently the 

 vertebrae in the American species are prolonged to a more limited ex- 

 tent into the upper lobe of the tail than in the European species," while 

 it supports his surmise that they may not be true Palseonisci, must be 

 regarded as in itself an indication of a somewhat more modern period. 

 It will be seen, therefore, that the affinities of this formation forbid our 

 yet assuming that any birds coexisted with the last races of primeval or 

 palaeozoic life. But the existence of creatures thus high in the scale of 

 animal organization, in times so remote as the earliest mesozoic epoch, 

 is a fact full of interest, and it is gratifying to the American geologist 

 to perceive that the views so early and candidly submitted in the face 

 of skepticism by Prof. Hitchcock, of the true origin of the bird-tracks, 

 are now universally admitted. That to him alone is due the merit of 

 being the original scientific discoverer of the nature of these impres- 

 sions, all who are familiar with the history of his labors must acknow- 

 ledge. Others before him had found specimens of the foot-marks, and 

 had shrewdly suggested that they may have been produced by birds, that 

 opinion having been entertained by a few persons even early in this 

 century, and Dr. James Deane, in drawing the attention of Prof. Hitch- 

 cock to some specimens, distinctly intimated the same belief as to their 

 origin. But conjecture in science is not discovery ; and if the principle 

 be a sound one, which awards the high title of " minister and inter- 

 preter" of nature to him only who, by extended, laborious and system- 

 atic observation and inductive reasoning, turns conjecture into demon- 



