Page:Scientific results HMS Challenger vol 18 part 1.djvu/1015

The membrane of the central capsule is commonly rather thin, and pierced by the twenty radial spines, meeting in the centre of the capsule. Between these lie innumerable small pores for the radiating pseudopodia; however, in many cases (and perhaps constantly) these pores exhibit a certain regular disposition. In many species the central capsule encloses Xanthellæ or symbiotic yellow unicellular Algæ. The nucleus becomes cleft very early in the majority of Dorataspida.

Synopsis of the Genera of Dorataspida.

II. Subfamily Diporaspida. Each radial spine with two opposite primary apophyses; therefore the whole shell with forty primary apophyses.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	I. Tribe Phractaspida. Twenty radial spines without lattice-plates; no normal pores.					$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	No by-spines,	349. Phractaspis.
								With by-spines,	350. Pleuraspis.
		II. Tribe Ceriaspida. Twenty radial spines all with lattice-plates produced by union of the branched apophyses of each plate.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Forty parmal pores (two in each plate)—no coronal pores in the plates.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Plates not dimpled, without network of crests.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	No by-spines,	351. Dorataspis.
								With by-spines,	352. Diporaspis.
								No by-spines, but free apophyses,	353. Orophaspis.
						Plates dimpled, with a network of crests.	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right\}\,}$	No by-spines,	354. Ceriaspis.
								With by-spines,	355. Hystrichaspis.
				Eighty to two hundred or more parmal pores (in each plate two aspinal and two to ten or more coronal pores).			$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	No by-spines,	356. Coscinaspis.
								With by-spines,	357. Acontaspis.
II. Subfamily Tessaraspida. Each radial spine with four crossed primary apophyses; therefore the whole shell with eighty primary apophyses.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	III. Tribe Stauraspida. Twenty radial spines all or partly without lattice-plates.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	All twenty spines without lattice-plates.			$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	No by-spines,	358. Stauraspis.
								With by-spines,	359. Echinaspis.
				Four plates with, sixteen without, lattice-plates.			$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	With by-spines,	360. Zonaspis.
				Twelve plates with, eight without, lattice-plates.			$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	With by-spines,	361. Dodecaspis.
		IV. Tribe Lychnaspida. Twenty radial spines all with lattice-plates (produced by union of the branched apophyses of each plate).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Eighty parmal pores (four on each plate)—no coronal pores in the plates.			$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$	No by-spines,	362. Tessaraspis.
								With by-spines,	363. Lychnaspis.
				One hundred and sixty to three hundred or more parmal pores (in each plate four aspinal and four to twelve or more coronal pores).			$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right\}\,}$	No by-spines,	364. Icosaspis.
								With by-spines,	365. Hylaspis.