Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 ( Kl'HALOPODA. D Fam. Nautilidae. The septa are simply bent and concave towards the anterior chambers. Line of suture simple, with a few large wavy curves or a lateral lobe. Siphon usually central ; shell orifice simple. Ortltnrarfix, shell straight. 0. regularise. Schl., calcareous strata of the North Germ?*! plain. Nautilus, shell coiled. N. pomj>ilii/.-< L., Indian Ocean. Fam. Ammonitidse. The septa much folded at the sides, always with lobe on the outer side, in the middle usua
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 ( Kl'HALOPODA. D Fam. Nautilidae. The septa are simply bent and concave towards the anterior chambers. Line of suture simple, with a few large wavy curves or a lateral lobe. Siphon usually central ; shell orifice simple. Ortltnrarfix, shell straight. 0. regularise. Schl., calcareous strata of the North Germ?*! plain. Nautilus, shell coiled. N. pomj>ilii/.-< L., Indian Ocean. Fam. Ammonitidse. The septa much folded at the sides, always with lobe on the outer side, in the middle usually convex forwards. Siphon on the outer side. Contains only fossil forms. Gonintites ri'tnn-xiix v. I»ueh., Cn-ti- tites nodosus Bosc., Ammonite* ciqn-iforniis v. Schl. Order 2.—DIBRANCHIATA.* Cephalopoda ivith two gills in the mantle cavity, eight arms bearing suckers or hooks, complete f'unnel and ink-sac. The Dibranchiata possess round the mouth eight arms provided FIG. 543.—Ai'i/Oiiauta argo (female), swimming. with suckers or hooks; in the Decapoda there are, in addition, two long tentacles placed between the ventral arms and the mouth. The cephalic cartilage constitutes a completely closed ring surrounding the central parts of the nervous system ; its slightly arched lateral parts serve for the support of the sessile eyes. There are only two gills in the mantle cavity and the same number of branchial vessels and kidneys. The funnel is closed. An ink-sac is usually present. The shell is in many forms completely absent; in others it is reduced to a horny or calcareous dorsal lamella. A spirally-coiled shell is * Chief works: Ferussac et d'Orbigny , also Verany
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