SYNOPSIS Or GENERA. liii 



Diagnosis. Carapace bivalved, prob- 

 ably with membranous attachment, no 

 distinct hinge-joint observable; valves 

 sub-ovate, semi-ovate, sub-quadrate or 

 trapezoidal; contracted in front, with 

 the end sharp or rounded above the median line of the valve; more or less 

 truncate. Rostrum a single lanceolate piece, the surface of which is chevron- 

 marked. Antennas (?) obscure. Dentate mandibles often apparent. Abdomen 

 many-jointed, with fourteen or more segments, of which from four to seven 

 extend beyond the carapace. Some or all of these segments bore small lamelli- 

 form branchial appendages. Post-abdomen consisting of a long caudal plate 

 which supports three caudal spines, namely : (1) a strong, tapering telson, thick 

 at the proximal end, with its trifid articulating surface resembling that in the 

 telson of Limulus, acute at the distal extremity and with the lateral margins 

 ornamented with spinules or setae ; and (2) two shorter, simpler, lateral append- 

 ages. The entire dorsal surface has alineate ornament, and the ventral margin 

 of the carapace a thin raised rim. (Jones and Woodward, Geol. Mag., Decade 

 iii, vol. ii, p. 385. 1885.) 



The species from the North American Devonian which arc referred to this 

 genus, are represented only by very incomplete specimens, which leave much 

 to be desired for an accurate determination of their generic relations. The 

 genus reached its culmination both in specific and individual development in 

 the Upper Silurian and probably became extinct in this country with the close 

 of the Devonian age. 



Genus ECH1NOCARIS, Whitfield. 1880. 



1863. Cemtiocaris, Hall. Sixteenth Rept. N. Y State Cab. Nut. Hist. 



1876. Cemtiocaris (Aristozoe), Hall. Illustrations of Devonian Fossils. 



1880. Echinocaris, Whitfield. Aiimt. Joui-n. Science. 



lS.si. Equisetides, Dawson ('). Quart. Journ. Geol. Soc, vol. xxxvii. 



n;s-j. Echinocaris, Packard. American Naturalist. 



I8S3. Echinocaris, Packard. Monog. N. Amer Phyllop. Crustac P 3. 



1884. Echinocaris, Beecher. Ceratiocaridae Chemung 1 and Waverly groups, Geol. Surv. Penna. Kept. 



1884. Echinocaris, Jones and Woodward Geolog. Mag. 



18S5. Echinocaris, Etheridge, Woodw LRDand Jones. Third Rept. on Fossil Phyllopoda. 



18S5. Echinocaris, Zittel Handb. d. Pateontologie. 



1885. Echinocaris, Novak. Sitzungsber. d. bohm. Gesellsch d. Wissensch. 

 18S5. Echinocaris, Clarke. Devon. Faunas Ontario Co. 



1886. Echinocaris, Clarke. Geol. Succession in Ontario Co. 



