簡介: 面線為後頰式(opisthoparian),尾部稍小於頭部。頭鞍往前漸窄,有二或三對頭鞍側溝。有眼圍及眼溝,眼脊有或無,眼睛的位置及大小不一。鞍前區有或無,固定頰upsloping,眼區寬,固定頰後區成三角形;自由頰亞三角形,頰刺結實,有時位於側面。胸部有10到13節,肋節平,末端刺狀,寬度為軸節1.5到2倍,中央有寬肋溝。尾部半圓形,軸部凸起,幾乎延伸至尾部邊緣,末端圓形有3到4個環節及一個末節,肋節5至6個,末端刺狀,長短不一,肋間溝不清楚,並往後漸模糊;肋溝寬;邊緣溝淺或消失;邊緣窄或無邊緣。殼表佈滿小顆粒或小刺。分佈於中寒武世到晚寒武世。DamesellidaeIntroductionExoskeleton opisthoparian, subisopygous. Glabella tapering, with 2 or 3 pairs of lateral furrows; palpebral rim and furrow present, eye ridges present or absent, eyes variable in size and position; preglabellar field present or absent; fixigenae upsloping, with wide palpebral areas, posterior areas triangular, of variable length; librigenae subrectangular, with stout genal spines, may be lateral in position. Thorax with 10 to 13 segments; axis convex; pleurae flat, ending in spines, 1.5 to 2 times width (tr.) of axis, with broad pleural furrow in center. Pygidium semicircular to transverse; axis convex, extending nearly full length to rounded end, with 3 or 4 axial rings and terminal; 5 or 6 pleurae ending in spines of variable length along margin, interpleural grooves obsolete except for faint anterior pair or line of granules, pleural furrows broad; border furrow shallow or obsolete, border narrow or absent. Surface with granules and small spines. Up.M.Cam. - Low.U.Cam .