A treatise on zoology . 469]. Ateleaspis, Trarpiair; Upper Silurian, Scotland (Fig. 177). Family Cephalaspidae. The head-region is covered dorsally by alarge shield with inturned edge, and ventrally with polygonal shield may bear a posterior median spine, and its posterior cornersmay be produced backwards into immense cornua (Eukeraspis). InAvchenasjns (Thyestes) the shield extends on to the trunk, several seriesof trunk-scales having apparently been incorporated into its hinder interorbital plate is fixed. Tlie cephalic shield is generally orna-mented with tubercles, and
A treatise on zoology . 469]. Ateleaspis, Trarpiair; Upper Silurian, Scotland (Fig. 177). Family Cephalaspidae. The head-region is covered dorsally by alarge shield with inturned edge, and ventrally with polygonal shield may bear a posterior median spine, and its posterior cornersmay be produced backwards into immense cornua (Eukeraspis). InAvchenasjns (Thyestes) the shield extends on to the trunk, several seriesof trunk-scales having apparently been incorporated into its hinder interorbital plate is fixed. Tlie cephalic shield is generally orna-mented with tubercles, and may bear tooth-like spines along its edge. A 204 CEP HA LA SPIDOMORPHI large fin-like lobe, covered witli scales continuous with the shield at itsbase, projects from each side of the body behind the cephalic shield inGefkalasins (Fig. 173 [505, 276, 326]). Ce2)halasjns, Ag., and Auchenaspis, Ag. {Tliyestes, Eich.); Upper Silurianand Devonian, Europe. Eukeraspis, Lank., Silurian, and Didymaspis,Lank., Devonian, Fig. 1 Diagrammatic restored o\\t\6 oi Atdeaspis tcsseUntu, Traq., the tail being turned so as toappear in profile. The orbits are shown near the middle of the head-shield, and in front ofthem the antorbital fossa and median pore. (After Traquair.) Family Tremataspidae. The almost smooth cephalic shield is con-tinuous round the sides on to the ventral surface. Ventrally, behind themouth, is an area covered by closely fitting plates, and between these andthe edge of the shield are a series of apertures, presumably interorbital plate is free ; the orbits roofless. Xo lateral flaps areknown [371, 325]. Tremataqns, Schmidt ; Upper Silurian, Eussia (Fig. 176), Order 3. ANASPIDA, An oider founded b}- Traquair [466] for the reception of twogenera of very aberrant structure from the Silurian rocks of Scot-land, Lasanius and Birkenia, to which has been added a less Avell-
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