. Cassell's natural history. Animals; Animal behavior. NATURAL HISTORY. calcareous labial appendages (Figs. 5, b, /) are therefore one of the most important features affecting the life and organisation of the animal inliabiting the shell, and their value as classificatory agents is apparent. Frequently preserved in a fossil state, there can be no doubt that they atford the simplest and readiest mode of determining the true relationship of one adult form of Brachiopod to another, and one that is infinitely preferable to the purely external characters of these very variable shells. In the subjoi
. Cassell's natural history. Animals; Animal behavior. NATURAL HISTORY. calcareous labial appendages (Figs. 5, b, /) are therefore one of the most important features affecting the life and organisation of the animal inliabiting the shell, and their value as classificatory agents is apparent. Frequently preserved in a fossil state, there can be no doubt that they atford the simplest and readiest mode of determining the true relationship of one adult form of Brachiopod to another, and one that is infinitely preferable to the purely external characters of these very variable shells. In the subjoined table of families, typical genera are placed first, and those represented solely by extinct forms are printed in italics :— Family. Gentra. LixGULin.'E . . Lingula, Glottidia, Lingulops, Obolus. ORDER TRETENTFR\TA -l Discixide . 'Diac\na.,Jimcmi&c!i,Trematis,lSiphoiioticta. . Crania, Craniops, Craniscus. imercIlidcE . . Trimerella, Moiiomorclla, Diiwholiis. CLISTENTERATA f Product idee I Strophomenidee . Pentamerida; I SpuiferidiB : Tehebratuliu-E ^ Frodiictm, Chonetes, Strophalosia. Strophomena, Orthis, Leptana. Fentamerus, Stricklandina. Spirifer, Spiriferina, Meristella, Athyris. Eliynchonella, Rliynchojmra, Atrypn. Terebratula, Waldheimia, Argiope, Laqueus, Kingenn. Thecidium. OEDER TRETENTERATA. FAMILY, THE LINGULID^.* The typical genus Lingula, one of the most ancient and pei-sistent of Brachiopoda, is, as might be expected, a very hardy animal. The hiugeless valves of the usually green or dusky brown shells are nearly equal in size, and it is from their elongated or tongue-like shape that the family name is derived (Fig. 7). The thick fleshy breathing organs with inwardly-directed spires are unsupported by any elaborate calcified process, but merely strengthened by a simple longitudinal plate or septum, rising from the centre of the dorsal valve. Professor Morse describes the American and Japanese species as living free and p
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Keywords: ., bookcentury1800, bookdecade1890, booksubjecta, booksubjectanimals
