Page:The Eurypterida of New York Volume 1.pdf/174

 side [ pl. 8, fig. 3] is ornamented with closely arranged semicircular to semilunar scales, largest and most prominent in the middle anterior region of the operculum, otherwise rather faint.

Ontogeny. has not yet afforded any growth stages as young as those of species from Otisville. The smallest specimens are already of neanic age. Hall figured an example [1859. v. 1, pl. 80, fig. 1] which without the telson spine, measures but 18 mm. An outline drawing [text fig. 33] and photograph [ pl. 4, fig. 1] of this specimen are here reproduced, and also the drawing of another small individual

[text fig. 34] given by Clarke in Zittel-Eastman, Text-book of Palaeontology, 1896, figure 1420. In the explanation of these figures Clarke pointed out the strongly anterior position of the eyes, relatively large size and length of the swimming legs and abrupt posterior contraction of the abdomen. The paucity of abdominal segments in figure 33 proves on investigation to be only apparent and due to the forcing of the posterior abdominal segments under the anterior. This secondary contraction of the body, apparently but accidental, or incidental to the process of molting, is also observed in some other young individuals. It is the principal cause of the contracted appearance of the abdomen.