562 Contributions to Invertebrate Palaeontologxj . 



of the Up. Held., Hamilton and Chemunp: groups, etc.), but has 

 been somewhat more nearly parallel on the margins, and has a 

 smoother shell. 



Formation and Locality. — In calcareous concretions of the Erie 

 shale, at Leroy, Lake Co., Ohio, accompanying the fossil entomo- 

 stracan from the same locality (next described). 



CRUSTACAEA. 

 PHYLLOPODA. 



In the 16th Rept. State Cab. New York there is represented a 

 peculiar bivalve crustacean from the Hamilton group of that State, 

 under the name of Ceratiocaris punctata ; and in the Illustra- 

 tions of Devonian Fossils, Plate 23, fig. 7, Section Crustacea, it is 

 repeated under the name Ceratiocaris (Aristozoe) punctata. 

 Among the fossils of the Erie shales of Leroy, Lake Co., Ohio, 

 similar forms have been detected, but specifically distinct from the 

 New York forms: Others, not yet described, have been observed 

 from the Hamilton and Chemung groups of New Nork. The Ohio 

 species here given, together with the Macrurian decapod and the 

 following observations on the genera with but slight modifications, 

 were published in the Am. Jour. Sci. and Arts for January, 1880, 

 as preliminary to this report. 



The fossils in question differ from the true types of Ceratiocaris 

 in so many particulars, and to so great an extent, that it is quite 

 impossible to include them under that genus. The reference to 

 Aristozoe Barr. is, however, still more erroneous, as the forms to 

 which that name is applied by its author are true Ostracoids, 

 having all their parts concealed within the carapace, as in Leper- 

 ditia and its allies; while the forms under consideration are pro- 

 vided with a bivalve, ov at least a two-sided carapace, which in- 

 closes the thoracic portions ; while the aV)domen and caudal parts 

 are naked, or not inclosed within this covering, and are more pro- 

 perly classed among the Phy]ioi)ods. 



That this latter character, the naked abdomen and caudal plate, 

 pertains to these organisms, is abundantly proven Ijy the Ohio 

 specimens now under consideration. The fossils are found inclosed 

 in small concretions; and there would l)e l)ut little chance for 

 specimens, or parts of specimens of different species, or less likely 



