A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . ttoms; some, it is inferred either fromthe absence or the extraordinary size of the eyes, in deepwater. In the growth of an individual trilobite of simplestructure, the free cheeks and the eyes borne by them areat first not seen on the upper surface of the head-shield. Asthe animal grows they appear at the edge, and graduallycome to occupy more and more of the upper surface. SomeTable-case early trilobites, however, such as Agnostus (Fig. 40 a),25. Harfes, and Tri
A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . ttoms; some, it is inferred either fromthe absence or the extraordinary size of the eyes, in deepwater. In the growth of an individual trilobite of simplestructure, the free cheeks and the eyes borne by them areat first not seen on the upper surface of the head-shield. Asthe animal grows they appear at the edge, and graduallycome to occupy more and more of the upper surface. SomeTable-case early trilobites, however, such as Agnostus (Fig. 40 a),25. Harfes, and Trinucleus, never reach this stage, and may beseparated as a Grade Hypoparia (under-cheeks) from thosein which the free cheeks are visible on the upper these latter the free cheeks may be confined to the fore- AETHROPODA—TRILOBITES. 85 part of the shield, as in Ccdyrnmenc, Staurocephalus (Fig. 40 c), Galleryand Phacops (Fig. 38), or they may stretch right back so as r^^i^^^^^^to include the genal angles, as in Olenus (Fig. 40 h), Para- , Triarthrus (Fig. 39), Ogygia, Brontcus, and Acidaspis. Table-case
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Keywords: ., bookauthorbr, bookcentury1900, bookdecade1900, booksubjectfossils
