TERMINOLOGY. PPP. 3 



18S0.—Frolessor 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 Ceratlocaris {Aristozoe) punc- 

 tahts. Hall. 



Tlie 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 tj^pe 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 proto- 

 type DiscixocARis, Woodward. For the reception of these 

 species he has erected the genera Spathiocaris and Dipter- 



OCARIS. 



1883. — In ''A Monor/7-apk of the North American Phil- 

 lopod Crustacea,^'' Dr. A. S. Packard reviews the genera of 

 the family ceratiocaridise and enumerates the described 

 species. 



Terminology. 



In the use of descriptive terms for the different mem- 

 bers of these crustaceans, it has been deemed advisable to 

 adhere to the establislied nomenclature, with perhaps a 

 few slight introductions and variations. The terminology 

 used is explained by the following diagram. 



It has been suggested tliat 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 

 furnislied with a rostrum the eyes were probably stalked. 

 None of the genera of the present paper have yielded any 

 evidence of a rostrjd plate, and it is doubtl'ul 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 



