SYNOPSIS OF 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, wdtli 
the end sharp or rounded above the median line of the valve; more or less 
truncate. Eostrum a single lanceolate piece, the surface of which is chevron- 
marked. Antennae (?) 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 setm ; and (2) two shorter, simpler, lateral append¬ 
ages. The entire dorsal surface has a lineate ornament, and the ventral margin 
of the carapace a thin raised rim, (Jones and Woodward, Geol. Mag., Decade 
hi, vol. ii, p. 385. 1885.) 
The species from the North American Devonian which are 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 ECHINOCARIS, Whitfield. 1880. 
1863. Ceratiocaris, Hall. Sixteenth Kept. N. Y State Cab. Nat. Hist. 
1876. Ceratiocaris {Anstozoe), Hall. Illustrations of Devonian Fossils. 
1880. Ecldnocaris, Whitfield. Amer. Journ. Science. 
1881. Eqtiisetides, Dawson (?). Quart. .Joui-n. Geol. Soc., vol. xxxvii. 
1682. Ecldnocaris, Packard. American Naturalist. 
1883. EcMnocaris, Packard. Monog. N. Amer. Phyllop. Crustacea. [P 3. 
1884. EcMnocaris, Beecher. Ceratiocaridie Chemung and Waverly groups, Geol. Surv. Penna. Kept. 
1884. Ecldnocaris, Jones and Woodward. Geolog. Mag. 
188,5. EcMnocaris, Etheridge, Woodward and Jones. Third Kept, on Fossil Phyllopoda. 
1885. EcMnocaris, Zittel Handb. d. Palieontologie. 
1885. EcMnocaris, Novak. Sitzungsber. d. bohm. Gesellsch d. Wissensch. 
1885. EcMnocaris, Clarke. Devon. Faunas Ontario Co. 
1886. EcMnocaris, Clarke. Geol. Succession in Ontario Co. 
