Page:Scientific results HMS Challenger vol 18 part 2.djvu/80

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THE VOYAGE OF THE H.M.S. CHALLENGER.

Synopsis of the Genera of Semantida.

I. Subfamily Semantiscida. Basal ring without typical, regularly disposed basal feet (no cortinar feet).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Only two, four, or six basal pores (no dorsal and ventral pores).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Two basal pores,	407. Semantis.
				Four basal pores,	408. Semantrum.
				Six basal pores,	409. Semantidium.
		Besides four basal pores, also apical pores or dorsal and ventral pores along the whole ring,			410. Clathrocircus.
II. Subfamily Cortiniscida. Basal ring with typical, regularly disposed basal feet (cortinar feet).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Three basal feet.		One odd caudal foot and two paired lateral feet,	411. Cortiniscus.
		Four basal feet.		Two sagittal and two lateral or pectoral feet,	412. Stephaniscus.
		Six basal feet.		Two sagittal, two pectoral, and two tergal feet,	413. Semantiscus.

Subfamily 1. Semantiscida, Haeckel.

Definition.—Semantida without typical basal feet or cortinar feet.

Genus 407. Semantis,^[1] n. gen.

Definition.—Semantida with two basal pores (or jugular pores), without typical basal feet.

The genus Semantis, the most primitive and the oldest of the Semantida, is of the greatest morphological interest, as the first form of Stephoidea which produces gates or pores by communicating branches, and therefore the probable ancestral form not only of this family, but of the greater number of all Stephoidea, and perhaps even of all Spyroidea and Cyrtoidea. Semantis arises from Archicircus by the production of two pairs of lateral branches from the basilar rod of the sagittal ring, one anterior pair of clavicular rods, and one posterior pair of coracal rods. By junction of the clavicular and coracal rod on each side arises a left and a right pore, the "jugular pore or jugular gate."

1. Semantis biforis, n. sp. (Pl. 92, fig. 2).

Sagittal ring obliquely ovate, nearly trapezoidal, with six pairs of short mammillated knobs or branches; dorsal rod straight, vertical, with two pairs of knobs, ventral rod strongly convex, also with

↑ Semantis = Signet-ring; σημαντίς.

[Nt26-1] Semantis = Signet-ring; σημαντίς.

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