Page:The Eurypterida of New York Volume 1.pdf/163

 of preoral chelicerae in place of antennae, already inferred by Schmidt, was demonstrated, [see restoration pl. 3, fig. 1]. The fifth segment of the second endognathite in the male carries a long, curved, tubular process [text fig. 32] which, by analogy with Limulus, Holm considered as a clasping organ employed during copulation. The epicoxite of the coxal segments before observed by Laurie in Slimonia and Pterygotus, was found in its proper position in Eurypterus and a circular perforation with very thin covering membrane has been observed close to the inner margin of the coxa of the fourth endognathite [see text fig. 12; pl. 7, fig. 6]. A corresponding organ in the living  was discovered by Holm on the coxae of the third and fourth endognathites near the epicoxite. On account of the structure of this organ and its position on that side of the coxa which is turned toward the outside, it was suggested that it has an auditory function. This structure has also been observed by Sarle in  [ pl. 62, fig. 5] and by the writers in   [ pl. 7, fig. 6]. A new organ was discovered, the endostoma. This consists of a small, thin, deeply emarginate shield, not clearly bounded on the sides, which formed the inner posterior margin of the mouth [ text fig. 13]. Further, the connection of the metastoma with the ventral integument of the cephalothorax by a doublure [ text fig. 14] was shown. The distinction between male and female genital appendages was clearly elaborated and the presence demonstrated of an interior paired, curved, tubular organ connected with the