SYNOPSIS OF GENERA. 
Iv 
in Aristozoe bear lateral carinae. It lias recently been shown by Novdk (Sitz- 
ungsber. d. Kl. bohm. Gesellsch. d. Wissensch, Jahrg. 1885,) that the species 
Bactropus longipes, Barrande, is probably the posterior abdominal somite of 
Aristozoe regina, and that the Ceratiocaris debilis, Barrande, may prove to be the 
telson spine of the same species. This spine is longitudinally ridged and bears 
a row of short prickles along each lateral margin. The genus Pti/chocaris, 
Novhk, 1885, from the same beds as Aristozoe, presents an intermediate group 
of forms in which the lateral carina is present, but in the arrangement of the 
anterior nodes it differs from both Echinocaris and Aristozoe. The points of 
similarity in Aristozoe and Ptychocaris with Echinocaris are of interest as the 
former genera antedate Echinocaris in paloeozoic faunas, being characteristic of 
the Etage F, or Hercynian Fauna of Kayser and Novak, while the genus 
Echinocaris is limited to middle and upper Devonian formations, and as yet 
known is exclusively American in its distribution. 
Genus ELYMOCARIS, Beecher. 1884. 
1884. Elymocans, Bebchek. CeratiocavidEe Chemung and Wavei-ly groups, Geol. Surv. Penna. Kept. P 3. 
188o. Elymocaris, Etheridge, Woodward and Jone.s. Third Kept. Committee Foss. Phyllop. 
1885. Elymocaris, Zittel. Handb. d. Palseontologie. 
Diagnosis. Carapace bivalvular, hinge-line straight and extend¬ 
ing nearly the entire length of the valves. Outline elongate-sub- 
quadrangular or sub-ovate. Surface gently and evenly convex. 
Cephalic region smooth or marked by two low broad nodes; optic 
node usually distinct. Rostrum absent or not observed. Abdo¬ 
men composed of two naked segments. Post-abdomen with a very 
short caudal plate to which are articulated a broad, convex and 
rapidly tapering telson and two short lateral spines which are 
crenulated along their inner margins for the attachment of the setae. 
Genus TROPIDOCARIS, Beecher. 1884. 
1884. Tropidocaris, Beecher. Ceratiocaridse Chemung and Waverly groups, Geol.Surv. Penna.Kept. P 3. 
1884. Tropidocaris, Etheridge, Woodward and Jones. Third Rept. Committee Foss. Phylloii. 
1885. Tropidocaris, Novak. Sitzungsber. bohm. Gesellsch. d. Wissensch. 
1885. Tropidocans, Zittel. Handb. d. Palaeontologie. 
