Page:Scientific results HMS Challenger vol 18 part 1.djvu/330

Synopsis of the Genera of Stylosphærida.

I. Subfamily Xiphostylida. (Spherical shell simple.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Polar spines free, without connecting ring on the distal ends.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Both spines equal,	45. Xiphosphæra.
				Spines different in size or form,	46. Xiphostylus.
		Both polar spines united by a circular or elliptical ring,			47. Saturnalis.
II. Subfamily Sphærostylida. (Two concentric spheres.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Polar spines free.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Both spines equal,	48. Stylosphæra.
				Spines different in size or form,	49. Sphærostylus.
		Both polar spines united by a circular or elliptical ring,			50. Saturnulus.
III. Subfamily Amphistylida. (Three concentric spheres.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Polar spines free.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Both spines equal,	51. Amphisphæra.
				Spines different in size or form,	52. Amphistylus.
		Both polar spines united by a circular or elliptical ring,			53. Saturninus.
IV. Subfamily Cromyostylida. (Four concentric spheres.)	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$	Polar spines free.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Both spines equal,	54. Stylocromyum.
				Spines different,	55. Cromyostylus.
V. Subfamily Caryostylida. (Five or more concentric spheres.)	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Polar spines free.		Both spines equal,	56. Caryostylus.
VI. Subfamily Spongostylida. (Spherical shell partially or wholly of a spongy structure.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Shell a solid spongy sphere without central medullary shell,			57. Spongolonchis.
		In the centre of the spongy sphere one or two medullary shells.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	One central medullary shell,	58. Spongostylus.
				Two concentric medullary shells,	59. Spongostylidium.

Subfamily Xiphostylida, Haeckel, 1881, Prodromus, pp. 449, 450.

Definition.—Stylosphærida with one simple spherical lattice-shell.

Genus 45. Xiphosphæra,^[1] Haeckel, 1881, Prodromus, p. 450.

Definition.—Stylosphærida with one single lattice-sphere and two free spines of equal size and form.

The genus Xiphosphæra is the most simple form of all Stylosphærida, and may be regarded as the common ancestral form of this family. On the surface of a simple

1. Xiphosphæra = Sword-sphere; ξίφος, σφαῖρα.