. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world. nct). The Aspidocephalt (also called Osteostraci)have bone-corpuscles in the shields, and theshield of the back is of one piece, withoutlateral line-channels or sense-organs. The orderincludes four families, Atcleaspidce (extinct),Ccphalaspidce (extinct), Thyestidce (extinct), Class Arthrodires.— Another group of ex-tinct mailed fishes is known as Arthrodira(ipOpov, joint; Sup-f), neck). In this groupjaws are developed, but of peculiar chara
. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world. nct). The Aspidocephalt (also called Osteostraci)have bone-corpuscles in the shields, and theshield of the back is of one piece, withoutlateral line-channels or sense-organs. The orderincludes four families, Atcleaspidce (extinct),Ccphalaspidce (extinct), Thyestidce (extinct), Class Arthrodires.— Another group of ex-tinct mailed fishes is known as Arthrodira(ipOpov, joint; Sup-f), neck). In this groupjaws are developed, but of peculiar character,the mandibles being regarded as mere der-mal elements, not forming part of the skele-ton. The head in all the species is covered witha great bony helmet. Behind this on the nape isanother large shield, and between the two istypically a hinge-joint, which has been comparedto the hinge of a spring-beetle (elater). Someof these plates are traversed by sensory whatever is known of the internalstructure, and as the skeleton is soft, the back-bone notochordal, there is no trace of shoulder-girdle, nor any certain evidence of limbs,.
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Keywords: ., bookcentury1900, bookdecade1900, bookidamericanauni, bookyear1903
