SYNOPSIS OF GENERA. lv 



in Aristozoe bear lateral carinas. It has recently been shown b\ Novak (Sitz- 

 ungsber. d. Kl. bohm. Gesellsch. d. Wissensch. Jahrg. L885,) thai the species 

 Badropus 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 hears 

 a row of short prickles along each lateral margin. The genus Ptijchocaris, 

 Novak, 1885, from the same beds as Aristozo'e, 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 palaeozoic 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 yel 

 known is exclusively American in its distribution. 



Genus ELYMOCARIS, Beechee. 1884. 



iss4. Elymocaris, Beecher. Ceratiocaridse Chemung and Waverlj groups, Geol. Surv. Penna.Rept. l':i. 

 18S5. Elyiaoearis, Etheridge, Woodward and Jones. Third Kept. Committee Foss. Phyllop. 

 1885. Elymocaris. Zittel. Handb. d. Palaeontologie. 



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 set*. 



Genus T R P I D C A R I S, Beecher. 1884. 



1884. Tropidoearis, Beecher. Ceratiocaridai Chemung and Waverl; • l.Surv.Penna.Rept,P3. 



1884. Tropidoearis, Etheridge, W ward and Jones. Third Rept. Committee Foss. Phyllop. 



1885. Tropidoearis. Novak. Sitzungsber. bohm. Gesellsch. d. Wissi nsch. 

 1885. Tropidoearis, Zittel. Handb. d. Palseontologie. 



