nautilidæ

pl. [Lat. nautil (us); fem. pl. adj. suff. -ide.] 1. Zool .: A family of Tetrabranchiate Cephalopods. Sutures of the shell simple; the siphuncle central, sub-central, or near the concavity of the curved shells; simple. By some naturalists it is divided into two sub-families, but the only recent genus is Nautilus (q. v.). 2. Paleont.: The Nautilide proper have gradnally decreased from the Paleozoic, through the Secondary and Tertiary periods, to the present day. nâu -từ-161d, a. & s. [ Gr.nautilos =the nautilus, and eidos =form, appearance.] A. As adj .: Resembling a nautilus. B. As subst.: That which has the form or appearance of a nautilus.