spirula

[Mod. Lat., dim in. from spira =a spire (q. v.).] Zool.: The sole genus of the family Spirulidæ (q. v.), with three species from all the warmer seas. Shell vertical in the posterior part of the body, with the involute spire toward the ventral side. The last chamber contains the ink-bag, and is not larger in proportion than the rest; its margin is organically connected. Body oblong, with minute terminal fins; mantle supported by a cervical and two ventral ridges and grooves, arms with six rows of minute cups, tentacles elongated, funnel valved. The shells are common, and a few specimens are cast on shore every year by the Gulf Stream, but the animal is exceedingly rare. spir-û-11-dæ, s. pl. [Mod. Lat. spirul ( a ); Lat. fem. pl. adj. suff. -ide.] Zool.: A family of Cephalopod a; shell nacreous, discoidal, whorls separate, chambered, with a ventral siphuncle.