Page:Scientific results HMS Challenger vol 18 part 2.djvu/318

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

Synopsis of the Genera of Tripocyrtida.

I. Subfamily Sethopilida. Terminal mouth of the thorax a simple wide opening.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	A. Three radial ribs (or cortinar rods) partly or completely enclosed in the wall of the thorax. No latticed vertical cephalic wings.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	a. Three thoracic ribs prolonged into three terminal feet.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Cephalis with a horn.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Feet solid,	534. Dictyophimus.
								Feet latticed,	535. Tripocyrtis.
						No horn, feet solid,			536. Sethopilium.
				b. Three thoracic ribs prolonged into three lateral wings.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Thorax perfectly latticed.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	With horn,	537. Lithomelissa.
								No horn,	538. Psilomelissa.
						Thorax with spongy framework,			539. Spongomelissa.
						Thorax with three large lateral holes between the three ribs,			540. Clathrocanium.
				c. Three thoracic ribs completely enclosed in the wall of the flat thorax	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Peristome simple, smooth,			541. Lamprodiscus.
						Peristome with a corona of spines,			542. Lampromitra.
		B. Three radial ribs enclosed in the wall of the thorax and connected with the cephalic horn by three latticed vertical wings.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	a. Thorax completely latticed	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	No frontal horn (four spines),			543. Callimitra.
						With frontal horn (five spines),			544. Clathromitra.
				b. Thorax with three large lateral holes between the three ribs. No frontal horn,					545. Clathrocorys.
		C. Three radial beams (or cortinar rods) perfectly free, not enclosed in the wall of the thorax.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Three beams outside the thorax, arising freely from the collar stricture (no cephalic hole),					546. Eucecryphalus.
				Three beams inside the thorax. Cephalis with a large apical hole,					547. Amphiplecta.
		D. Three radial terminal feet on the peristome (the three original lateral ribs are lost).			$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Feet solid,			548. Lychnocanium.
						Feet latticed,			549. Lychnodictyum.
II. Subfamily Sethoperida. Terminal mouth of the thorax closed by a lattice-plate.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Three divergent ribs (or cortinar rods) enclosed either in the wall or in the cavity of the thorax.			$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Three ribs enclosed in the lattice-wall of the thorax,			550. Sethopera.
						Three internal rods in the cavity of the thorax,			551. Lithopera.
		Three divergent free lateral wings (as prolongation of the three ribs) on the sides of the thorax.			$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	Three solid lateral spines.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Cephalis with horn,	552. Micromelissa.
								No horn,	553. Peromelissa.
						Three latticed lateral wings. With horn,			554. Sethomelissa.
		Three free terminal feet (on the base of the thorax).			$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Three feet solid,			555. Tetrahedrina.
						Three feet latticed.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Shell without external mantle,	556. Sethochytris.
								Shell with an arachnoidal mantle,	557. Clathrolychnus.