98 CORRELATION OF GEOLOGICAL FAUNAS. [bull. 210. 
the Oneonta sandstone was recognized and named in 1886 a as the 
"Leiorhynchus globuliformis stage of the Middle Devonian fauna." 
The gibbous form of Leiorhynchus, under the name Atrypa globuli- 
formis, was noted by Vanuxem as existing in myriads in the "Che- 
mung group" of the third district, "numerous localities abounding 
with it." 6 
The close relationship between the species so abundant in the are- 
naceous strata overlying the Oneonta sandstones of Chenango and 
Otsego counties and the common flattened form Leiorhynchus mesi- 
costale was recognized by Hall. c 
The presence of the species in the Ithaca formation was noted in 
1884, d also the fact that in the rocks about Ithaca the form called 
Leiorhynchus mesicostale was found in the softer argillaceous shales, 
"while in the more arenaceous beds the convex forms L. globuli- 
forrne and L. kellogi appear." The great variability of the specimens 
in any handful led to the belief there expressed — 
that the representatives of the genus Leiorhynchus, found in the Devonian of New 
York at least, offer no better claim to specific distinction than do the various 
forms of Atrypa reticularis, although the variations of form and the relative prev- 
alence of certain variations are valuable and, we believe, sensitive indications 
of changed conditions of environment. 
The association of gibbosity of form with sandy sediments gave 
occasion for expecting the species to appear in the sediments follow- 
ing the Oneonta sandstone in the Chenango Valley, and that this 
species should appeal- there in place of Leiorhynchus mesicostale 
was looked upon not as indicative of a new species, but as evidence 
of changed conditions of environment modifjdng varietally the com- 
mon Ithaca form. 
Another fact has been observed in the course of these studies — 
Leiorhynchus occurs very often in the rocks among the first species of 
brachiopods to appear in running up a section after a barren place in 
the strata. This was interpreted as an indication that the genus was 
adapted to live in conditions unfavorable to the life of most of the 
brachiopods. It was noticed in the Chenango Valley region that Lei- 
orhynchus globuliforme was among the earlier species to appeal* 
above the sands and flags (nearly barren of marine invertebrates) 
above the horizon of the Oneonta sandstone. The fact that the spe- 
cies appeared in the Ithaca formation associated with the characteris- 
tic species of that formation, and was particularly associated with the 
hard sandstone beds, which were distinctly purple in color, led to the 
suspicion that this Leiorhynchus globuliforme fauna was a represen- 
tative of the Productella speciosa fauna of the Ithaca formation, but 
a little later in age. 
This theory of a shifting of the fauna across central New York from 
aProc. Am. Assoc. Adv. Sci.. Vol. XXXIV, p. 226. 
6 Geology of Third District of New York, p. 182. 
c Paleontology New York, Vol. IV, p. 364. 
tfBull. U. S. Geol. Survey No. 3, p. 16. 
