xxxviii SYNOPSIS OF GENERA. 
1872. Lichas, Barrande. Suppl. Syst. Silur. du Centre de la Boh^me, vol. i. 
1872. Lichas, Kayser. Zeitschrift der dentsch. geolog. Gesellschaft. 
1874. Lichas, Steinhardt. In preussisch. Geschieb. gef. Trilobiten. 
1874. LAclias, Billings. Canadian Naturalist and Geologist. 
1878. Lichas, Miller. Jour. Cincinnati Soc. Nat. Hist. 
1879. Lichas, Hall. Twenty-eighth Kept. N. Y. State Mus. Nat. Hist. 
1880. Lichas, Novak. Sitzungsber. d. Kongl. bohin. Gesellsch. d. Wissenschaften. 
1882. Lichas, Brogger. Silur. etagen 2 und 3, im Kristianiageb. und auf Ekei‘. 
1884. Lichas, Tornquist. Undersok. ofv. Siljanourad. Trilobit fauna. 
1885. Lichas, Schmidt. Mem. de I’Acad. imp. de St. Petersbourg. 
1886. Lichas, Barrois. Ann. de la Societe geol. dn Nord. 
1887. LAchas, Foerste. Bulletin Denison University. 
1888. Lichas, Frech. Zeitschr. der deutsch. geol. Gesellsch. 
Diagnosis. Body broadly oval. Cephalon transverse. Glabella convex and 
subdivided by two longitudinal furrows, which are produced by the union of 
the proximal extremities of the lateral furrows. Eyes situated somewhat pos¬ 
teriorly. Facial sutures beginning on the posterior margin, near the genal 
angles, passing forward from the eyes in sub-parallel lines to the anterior mar¬ 
gin. Hypostoma sub-quadrate, with a deep reentrant curve on the posterior 
margin. Centrum gently convex. Thorax composed of eleven segments. Pleurae 
silicate and produced into acute terminations. Pygidium sub-triangular, gently 
convex. Axis very short, with but two or three annulations. Pleurae broad, 
sulcate. Margins lobate. 
Sub-genus TER AT ASP IS, Hall. 1863. 
1862. Lichas, Hall. Fifteenth Kept. N. Y. State Cab. Nat. Hist. 
1863. 'Lerataspis, Hall. Sixteenth Kept. N. Y. State Cab. Nat. Hist. 
1876. Acidaspis {Terataspis), Hall. Illustrations of Devonian Fossils. 
Diagnosis. Frontal lobe of the glabella 
ellipsoidal, longitudinally and transversely 
bisymmetrical, strongly and equally con¬ 
stricted on all sides. First and second 
lateral lobes coalesced and strongly spinose 
at their summit; third lateral lobe obsolescent or extinct. Glabellar area be¬ 
tween the anterior lobe and occipital ring much depressed. Occipital ring broad, 
bearing strong spines or baculate tubercles. Pygidium with one annulation upon 
the axis, two or three upon the pleurse, and bearing eight long, recurved, simple 
or compound marginal spines. 
