. Annual report. New York State Museum; Science; Science. l80 NEW YORK STATE MUSEUM It is interesting to note that Girty finds this species, or one prac- tically inseparable from it, in the Moorefield shales of Arkansas. Composita dawsoni (Hall & Clarke) Athyris subtilita Davidson. Quart. Journ. Geol. Soc. Lond. 19, p. 170, pi. 9, fig. 4, 5, (not A. subtilita Hall) 1863. Quoted by Dawson, Acad. Geol, p. 290, fig, 88a-c, 1868. Seminula dawsoni Hall. 13th Ann. Rept. N. Y. State Geol., p. 652, pi. 47, fig. 32-34, 1894; 14th Rept., p. 359, pi. 9, fig. 14-16, 1897. The specimens referred to thi
. Annual report. New York State Museum; Science; Science. l80 NEW YORK STATE MUSEUM It is interesting to note that Girty finds this species, or one prac- tically inseparable from it, in the Moorefield shales of Arkansas. Composita dawsoni (Hall & Clarke) Athyris subtilita Davidson. Quart. Journ. Geol. Soc. Lond. 19, p. 170, pi. 9, fig. 4, 5, (not A. subtilita Hall) 1863. Quoted by Dawson, Acad. Geol, p. 290, fig, 88a-c, 1868. Seminula dawsoni Hall. 13th Ann. Rept. N. Y. State Geol., p. 652, pi. 47, fig. 32-34, 1894; 14th Rept., p. 359, pi. 9, fig. 14-16, 1897. The specimens referred to this species are not very abundant, are distorted and poorly preserved. It can not be stated that they certainly belong to the species to which they are here referred, though there appears to be little doubt of it. Nucula iowensis White & Whitfield var. magdalenensis nov. Shell minute, triangular in outline, very ventricose. Beaks nearly terminal posteriorly, little elevated; dorsal border slightly arcuate, sloping forward to the pointed anterior end which rounds abruptly into the nearly straight but gently con- vex Ventral margin making an abrupt turn upwards at the posterior extremity. Nucuia iowensis var. magda- Posterior margin truncated from beaks lenensis nov. Cardinal view x 5. A ~, r , .. Surface of left valve x 4 to' ventral extremity, burface marked by regular concentric crenulated striae separated by depressions of about equal width. Dimensions. Length, about 4 mm; height, mm; convexity, 2 mm. Remarks. Winchell's description of N. iowensis is followed by these remarks: " The shell appears to be subject to considerable variation at dif- ferent stages of growth; young specimens often being distinctly triangular, with the posterior end very short, and the basal margin but little arched, while the old specimens are subovate and the posterior end more prolonged. This description of young indi- viduals tallies very closely with the species in hand which may be a
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