454 GEOLOGY OF OHIO. 



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 Illustrations of Devonian 

 Fossils, Plate, XXIII, fig. 7, Section Crustacea, it is repeated under the 

 name Ceratiocaris (Aristozoe) ptmctata. Among the fossils of the Erie 

 shales of Leroy, Lake county, Ohio, similar forms have been detected, 

 but specifically distinct from the New York forms : Others, not yet de- 

 scribed, have been observed from the Hamilton and Chemung groups of 

 New York. 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 preliminar}^ 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 Ostracods, having all their parts con- 

 cealed within the carapace, as in Leper ditia and its allies ; while the 

 forms under consideration are provided with a bivalve, or at least a two- 

 sided carapace, which incloses the thoracic portions ; while the abdomen 

 and caudal parts are naked, or not inclosed within this covering, and are 

 more properly classed among the Phyllopods. 



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

 tains to these organisms, is abundantly proven by the Ohio specimens 

 now under consideration. The fossils are found inclosed in small con- 

 cretions; and there would be but little chance for specimens or parts of 

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

 distinctly related generic forms, to be inclosed in the same small con- 

 cretion ; so we may safely conclude, that, where parts or fragments of 

 individuals of corresponding size are found in the same concretion, they 

 are parts of one individual or at most, of the same species. In the con- 

 cretions in question, there are two examples where parts of the naked 

 abdomen and caudal plate with its accompanying spines, are imbedded in 

 the concretion together with the carapace which I have classed as of the 

 s ame species. This I consider as ample proof that the parts belong to 

 the one individual ; and that the animal of which they are the remains, 

 was provided with a naked body and spinose caudal appendage as in 

 Ceratiocaris. It is also, stated in the Illust. Dev. Foss., that one specimen 

 resembling C. punctata, has been found with a body similar to that called 

 C. armata attached to the carapace, showing their individual relations. 



The several species above mentioned, while differing greatly from 

 Ceratiocaris, possess features in common which at once characterize 



