. Zoology : for students and general readers . Zoology. PTEROPODA. 259. - iytyliola vitrea.—Afier Verrill. A common form, occurring at the surface in harbors north of Cape Cod, as well as many miles off shore, is Spiri- alis Gouldii Stimpson, the shell of which resembles a conical Helix, f he largest form on the eastern coast of North America, extending from New York to the polar seas, is the beautiful Clione papillon- acea of Pallas, which has a head and lin- gual ribbon. It is rare on the coast of New England, but abundant from Labra- dor northward. We have observed it rising and falling in
. Zoology : for students and general readers . Zoology. PTEROPODA. 259. - iytyliola vitrea.—Afier Verrill. A common form, occurring at the surface in harbors north of Cape Cod, as well as many miles off shore, is Spiri- alis Gouldii Stimpson, the shell of which resembles a conical Helix, f he largest form on the eastern coast of North America, extending from New York to the polar seas, is the beautiful Clione papillon- acea of Pallas, which has a head and lin- gual ribbon. It is rare on the coast of New England, but abundant from Labra- dor northward. We have observed it rising and falling in the water between the floe-ice on the coast of Labrador. It is an inch long, the body fleshy, with no shell, the wings being rather small. The larvae of the Pteropods pass through a trochosphere stage, being, as in C'avolina, spherical, with a ciliated crown. It after- wards assumes a veliger form. Fig. 184 represents a worm- like, segmented, Pteropod larva, the adult of which is unknown. In other genera the larvas are annulated, resem- bling the larvae of Annelides. The Pteropods are, in some degree, a generalized type. They have a wide geographical distribution and a high antiquity; forms like CavoUna, viz.: Theca, Conularia, Tentaculites, CornuUtes, etc., dating back to the palaeozoic formation ; Theca-like forms {Pugmnculus and Hyolithes) occurring in the primordial rocks. Order 3. Gastropoda.—This great assemblage of moUusks is represented by the sea-slugs, limpets, whelks (Figs. 185-188), snails, and ptero- slugs. The head is quite distinct, bearing one, and sometimes, as in the land-snails, two pairs of tentacles, with eyes either at the leases, or at the ends of the tentacles, or, as in Trivia californica (Fig. 189), they are situated on projections near the base of the tentacles. All the Gastropods move or glide over the surface by the broad creeping-disk, a modiflcation of the foot of the clam. Fig. 184, pod larva. Please note that these images are extracted from
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
