Page:Second Geological Survey of Pennsylvania Report of Progress PPP.djvu/23

 size, less conspicuous and differently located nodes, and in the more simple character of the ornamentation.

This well-marked species occurs in the shales of the Hamilton group at several localities in the central portion of the State of New York. It is here introduced for the sake of comparison, and for a better elucidation of the characters of the following species. I am indebted to Professor James Hall, for the permission to examine and figure specimens of this species, belonging to the New York State Museum, at Albany. These collections furnish conclusive evidence of the identity of the abdomen and telson, referred to Ceratiocaris armatus, with the carapace described as ''Ceratiocaris? punctatus''.

The specimen Fig. 16, Plate I, is the only one yet observed in this genus showing the mandibles and their position. In 1865 Professor Henry Woodward, of the British Museum, described and figured a specimen of Ceratiocaris papilio which preserved the mandibles and showed the position which they occupy in the carapace. These two examples add materially to our knowledge of the characters of this group, and with the nearly entire specimens described in this and in the succeeding species, furnish us with material for a comparison with their recent ally—Nebalia.

Some of the specimens are covered with numerous examples of a small species of Crania, which from the perfect preservation of the Echinocaris were probably attached during the life of the crustacean. The shales carrying these remains are highly charged with other fossils, among which are fragments of fishes, Beyrichia, Leperditia, Phacops, Homalonotus, Orthoceras, Nautilus, Loxonema, Pleurotomaria, Bellerophon, Platyostoma, numerous species and genera of lamellibranchiata, with a few species of brachiopods and bryozoans.

Associated with numerous specimens of E. punctata are frequently found mandibles or jaws of the form represented in Figs. 9–11 of Plate II. These are evidently of crustacean origin and although somewhat similar in form to the mandibles undoubtedly belonging to E. punctata, they probably