bdi SYNOPSIS OF GENERA. 



1852. Posidojunnya, Pacht. Ueb. Dimerocnnites. 



1852. /' a, Kbtorga. <;•■'■ lt n . Karte Gouvern. Petersbourg. 



1855. Estheria, Jones. Quart. Journ. Geol. Society. 



1858 /• ■■, ot, Vok Helmersen. Geogn. Untersuch. Mi ttl. Gouvern. Russl. 



L859. Estheria, Jones. Quart. Journ. Geol. Society. 



I860. Asmusia, Pander. Monogr. der Saurodipterinen. 



LS62. Estheria, Jones. Monogr. Foss. Estherias. 



1882. Estheria, Ci wikk. Amer. Journ. Science. 



[883. Estheria, Packard. Monogr. North Amer. Phyllop. Crustacea. 



Diagnosis. Carapace bivalvular, the outline of each valve being sub-circular, 

 obliquely oval or sub-quadrate. Beaks generally anterior, sometimes sub- 

 mit ral. Dorsal or hinge-line straight, shorter than the greatest length of the 

 valves. Surface rarely smooth, usually with concentric lines of growth, the 

 interstitial spaces being often ornamented with a fine punctate or reticulate 

 sculpture. Test very thin. 



Genus SCHIZODI SCUS, nov. gen. 



Diagnosis. Carapace bivalvular, the valves readily separable along the hinge. 

 Outline circular or ovate, narrowing posteriorly. Surface convex or depressed, 

 elevated at the beaks which are prominent, slightly incurved, and situated 

 anteriorly. Hinge-line equaling in length the greatest diameter of the cara- 

 pace ; edges parallel and not gaping at either extremity. Surface ornamented 

 by regularly concentric wrinkles. 



ORDER, CIRRI FED I A. 



Family, Balanid.e. 



Genus PROTOBALANUS, nov. gen. 



Diagnosis. Shell ovate about the basis; composed of twelve plates of which 

 the carina is largest and most elevated. Rostrum small; lateralia five on each 

 side ; radial areas between the lateralia broad ; scutum and tergum not known. 

 i leneral surface depressed convex. 



