. Bulletin - New York State Museum. Science. REPORT OF THE STATE PALEONTOLOGIST 1902 1041 rounded at the bottom, and somewhat narrower than is usual in this species. It is flanked by about four rounded plications on each side, which widen gradually toward the front of the shell. The brachial valve has four plications on each side of the central fold, the fourth being very short and much fainter than the others. The Fig. 5 spirifer vanuxemi, median depression along the top of pedicle valves _ . i . the fold is marked in some cases, in others it does not occur at all. The plications, as well as
. Bulletin - New York State Museum. Science. REPORT OF THE STATE PALEONTOLOGIST 1902 1041 rounded at the bottom, and somewhat narrower than is usual in this species. It is flanked by about four rounded plications on each side, which widen gradually toward the front of the shell. The brachial valve has four plications on each side of the central fold, the fourth being very short and much fainter than the others. The Fig. 5 spirifer vanuxemi, median depression along the top of pedicle valves _ . i . the fold is marked in some cases, in others it does not occur at all. The plications, as well as the sinus and fold, extend to the apex. So far as I have been able to examine specimens of S. vanuxemi typical of the Manlius of eastern New York, the de- pression in the median fold of the brachial valve, where it occurs, is a feature of maturity rather than characteristic of the entire shell. In a few cases the depression in the fold can be traced nearly or perhaps quite to the apex of the valve. When the depression is well marked, the plications appear sharper and comparatively narrower. They also extend farther up the beak. On the other hand, it appears to be the case that, when the depression in the fold is faint or absent, the plications are less defined and near the apex become obsolete. Neverthe less, there are individuals in which the depression in the fold and the broadly rounded plication occur together. Finally, individuals occur (as figured by Hall) in which the apical por- tion is free from plications, these beginning part way down. In this case they are, so far as observed, broad and rounded. The young individuals of the species are in all cases marked by less pronounced and fewer plications. In certain forms, which may be considered the more primitive representatives of the species, the young are practically free from plications, or if these occur, they are broadly rounded and low, one or two only occurring on each side of the fold or sinus. From these considera
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