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The only existing genus of tetrabranchiate cephalopods. About four species are found living in the tropical Pacific, but many other species are found fossil. The shell is spiral, symmetrical, and chambered, or divided into several cavities by simple curved partitions, which are traversed and connected together by a con…

les; as, the nidament capsules of certain gastropods; nidamental glands. See Illust. of Dibranchiata.

Belonging to the Nucleobranchiata. -- n.

Of or pertaining to the Nudibranchiata. -- n.

Any one of numerous species of freshwater pectinibranchiate mollusks, belonging to Paludina, Melantho, and allied genera. They have an operculated shell which is usually green, often with brown bands. See Illust. of Pond snail, under Pond.

One of the Pectinibranchiata. Also used adjectively.

Same as Lamellibranchia.

artilage; especially, one of the lower pharyngeals, which belong to the rudimentary fifth branchial arch in many fishes, or one of the upper pharyngeals, or pharyngobranchials, which are the dorsal elements in the complete branchial arches.

has one or two external openings through the nose in the higher vertebrates, and lateral branchial openings in fishes and some amphibias.

Same as Prosobranchiata.

arynx, lungs, heart, stomach, liver, and spleen, and, in fishes and many amphibia, to the branchial apparatus and also to the sides of the body.

A small European lamprey (Petromyzon branchialis); -- called also prid, and sandpiper.

An extensive division of pectinibranchiate gastropods, including those that have a long retractile proboscis, with the mouth at the end, as the cones, whelks, tritons, and cowries. See Illust. of Gastropoda, and of Winkle.

One of the Prosobranchiata.

Same as Pseudobranchia.

A divisiom of gastropods; the Pectinibranchiata.

xis and the tentacles are borne on a bilobed lophophore. It is the type of the order Pterobranchia, or Podostomata

and are regarded as olfactory organs. Called also dorsal tentacles. See Illust. under Pygobranchia, and Opisthobranchia.

A division of pectinibranchiate gastropods, having the head prolonged into a snout which is not retractile.

Same as Pellibranchiata.