. College collection of palaeontology. ANNELIDA. 89 CLASS ANNELIDA. The name Worms (Yermes) is popularly applied to all the diverse organisms of an elongated and segmented character, but tlie lowest forms, including the so-called intestinal or parasitic worms and the rotifers, are properly separated and form the ]ieterogeneous class Scolecida. The higher forms, included in this â class (annelida or annulata), have distinctly segmented cylindrical bodies, but without division into thorax and abdomen. When lateral appendages exist they are not jointed, nor articulated to the body. The nervous sy
. College collection of palaeontology. ANNELIDA. 89 CLASS ANNELIDA. The name Worms (Yermes) is popularly applied to all the diverse organisms of an elongated and segmented character, but tlie lowest forms, including the so-called intestinal or parasitic worms and the rotifers, are properly separated and form the ]ieterogeneous class Scolecida. The higher forms, included in this â class (annelida or annulata), have distinctly segmented cylindrical bodies, but without division into thorax and abdomen. When lateral appendages exist they are not jointed, nor articulated to the body. The nervous system is a chain of ventral ganglia; and a system of tubes (pseudohsemal vessels), containing a colored plasma, takes the place of heart and blood vessels. Respiration ma}^ be through the skin, as in the Leech and Earthworm (Abranchiata), or by means of external gills, as in the marine forms (Branchiata). Worms have left traces in every deposit in the form of shelly coverings, burrows, or imprints. Worm-holes abound in the Pots- dam sandstones; they were made at tide-level, vertically, and often in pairs. The most common kind is the Scolithus linearis. Many supposed annelid borings and tubes have been named, the character of which are still uncertain. Serpula and Sjnrorhis seem to have existed since the Upper Silurian. No. 171. Scolithus linearis. Hall. These tubes were believed by Dr. Hall to be fucoid, but they are now gen- erally regarded as the borings of " Errant " annelids. The burrows are nearly straight and extend vertically through the neck. From the Potsdam Sand- stone, York, Penn. No. 173. Serpula. This still living genus secretes a long, shell- like tube of carbonate of lime, more or less tortuous, which are attached to some foreign body. It is one of the " Tubiculous " anne- lids; and its supposed tubes have been found in all the formations above the Lower Silurian. This specimen from the Quaternary, Palermo, Italy. Please note that these images
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