1880.—Professor R. P. Whitfield in 1880 (Am. Jour. Sci., vol. xix) described three allied species from the Devonian of Ohio and established the genus Echinocaris, which is to include also, the species Ceratiocaris (Aristozoe) punctatus, Hall.
The present paper furnishes one new species belonging to the genus Echinocaris and two related genera considered as new to science, under which are described four species.
Besides the crustaceans of the type of Ceratiocaris, Professor J. M. Clarke has shown (Am. Jour. Sci., Vols. xxiii and xxv, 1882–3,) that the Devonian series furnishes another distinct but allied group belonging to the prototype Discinocaris, Woodward. For the reception of these species he has erected the genera Spathiocaris and Dipterocaris.
1883.—In "A Monorgraph of the North American Phillopod Crustacea," Dr. A. S. Packard reviews the genera of the family ceratiocaridiæ and enumerates the described species.
Terminology.
In the use of descriptive terms for the different members of these crustaceans, it has been deemed advisable to adhere to the established nomenclature, with perhaps a few slight introductions and variations. The terminology used is explained by the following diagram.
It has been suggested that the so-called "optic spots" of McCoy and other authors may only be frontal bosses, and not connected with vision. In recent forms such as Apus there are three eyes one of which is double [Baird], other genera show one (double) or two. In the species furnished with a rostrum the eyes were probably stalked. None of the genera of the present paper have yielded any evidence of a rostral plate, and it is doubtful if such an appendage will be discovered. The tubercle, as indicated above, is one of the most constant features of the carapace in all of the species and must have a special significance. In a number of specimens examined, by the writer, under the microscope a subcircular depression is observed at or
