Page:The Eurypterida of New York Volume 1.pdf/248

 heart-shaped in the younger [ pl. 33, fig. 3]. The organ was slender and relatively long; in the larger specimen it extends, incomplete as it is, to the third sternite. The appendage of the second sternite has not been observed.

Ornamentation. The ornamentation of this species is characterized by the small size, but immense number and round circular form of the scales and tubercles. The carapace uniformly bears small tubercles, giving it a shagreen surface. The coxa, the metastoma and the muscular joints of the walking and swimming legs have somewhat larger scales most of which have the form of slightly tilted disks with the anterior segment cut away or submerged in the periderm, the posterior portion being raised. The tergite of a mature individual bears rather widely scattered, larger semicircular to low triangular scales which terminate rather abruptly or become fewer and smaller over the posterior doublures but continue on their overlapped anterior parts. On the sternites the scales are arranged in distinct bands, the anterior halves of the plates being covered with such a densely crowded mass of small semicircular scars that the naked eye fails to discern them. These increase in size to the middle of the sternite where they form a zone of larger semicircular to crescentic scars which are less densely arranged and become farther separated posteriorly until they almost entirely disappear above the doublure. Between these larger scales numerous small ones, often of microscopic size, are interspersed. The opercular plates differed from the other sternites in being almost entirely covered with the larger scales which are much more densely arranged than on the following plates, but are also lacking along the posterior border. The pentagonal and sagittate basal portions of the female genital appendage are ornamented like the opercular plate.

The postabdomen, as a whole, bears scales of the size and distribution of those on the tergites. They lengthen, however, posteriorly, approximately in proportion to the remarkable lengthening of these postabdominal segments until on the last segment they have become acutely pointed.