. Zoology : for students and general readers . Zoology. 108 ZOOLOGY. each side of which are attached a row of pinnules. Be- sides Pentremites are the typical genera Elmacrinus and EleatJierocrinus. Order 3. CystidecB.—This group is likewise extinct. In the fossil Pseudocrinus there is a short-jointed stalk, while in Caryocystites (Fig. 69) there is no stalk and no arms, the. Fig. 69.—Caryoa/s- iites, a Cyetidean.— Af tur Liitkeu. Fig. 71.—Aqelacrinus, a Cyetidean, on the shell of aBrachiopod.—After Llitkeu Fig. 70.—P^eudocH- nits, a Cyytidean,— After Liitkeu, body being angulo-spherical, compo
. Zoology : for students and general readers . Zoology. 108 ZOOLOGY. each side of which are attached a row of pinnules. Be- sides Pentremites are the typical genera Elmacrinus and EleatJierocrinus. Order 3. CystidecB.—This group is likewise extinct. In the fossil Pseudocrinus there is a short-jointed stalk, while in Caryocystites (Fig. 69) there is no stalk and no arms, the. Fig. 69.—Caryoa/s- iites, a Cyetidean.— Af tur Liitkeu. Fig. 71.—Aqelacrinus, a Cyetidean, on the shell of aBrachiopod.—After Llitkeu Fig. 70.—P^eudocH- nits, a Cyytidean,— After Liitkeu, body being angulo-spherical, composed of solid plates. The Cystideans (Figs. 69 to 71) originated in the Cambrian for- mation, attained their maximum development in a number of species in the Silurian, and became mostly extinct in the Carboniferous period. Class I.—CRINOIDEA. Spheriail or cup-shaped Echinoderms, wifnout a inadreporic plate, usii- ally attaclied by a jointed stem, a few free in adult life, with five arms sub- dividing into pinnulm; the amiulacral feet in the form, of tentacles arising around the mouth in the furrows of the calyx or situated on (lie jointed arms. In the Blastoidea and certain Cystideans the anas are ab- sent, hut the jnnnidm are usually present, though absent in Oaryocystites. Circulatory, water-vascular, and sexual organs much as in other Echino- derms ; tlie digestive caned ending in a distinct eccentric Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Packard, A. S. (Alpheus Spring), 1839-1905. New York : Henry Holt
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
