Dorataspida et Diploconida, Haeckel, 1862, Monogr. d. Radiol.,
pp. 404, 412.
Acanthophractida, Richard Hertwig, 1879, Organismus d. Radiol.,
pp. 25, 137.
Dorataspida, Diploconida, et Sphærocapsida, Haeckel, 1881,
Prodromus, p. 467.
Definition.—Acantharia with complete latticed shell.
The order Acanthophracta, the fourth order of Radiolaria, comprises all those Acantharia in which the acanthinic skeleton is a complete latticed or fenestrated shell, supported by radial spines arising from one common central point. By the possession of such a complete shell the Acanthophracta differ from their ancestral group, the nearly allied Acanthometra, which represent the older and simpler, first order of Acantharia. All Acanthophracta are Icosacantha (like the Acanthonida, their ancestral group), and possess twenty radial spines disposed according to the Müllerian law (compare above, p. [717]).
Johannes Müller, who first observed five representatives of this order, called a part of them "Acanthometræ cataphractæ," and united these with the true Acanthometra (Acanthometra costata and Acanthometra cataphracta; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 12, 49). Another part was united by him with the true Haliomma (Haliomma echinoides, Haliomma hystrix, Haliomma tabulatum; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 36, 37). He supposed that these latter formed the immediate transition from the true Acanthometra to the true Haliomma, and that their skeleton was siliceous.
In my Monograph (1862, p. 412) I founded a separate subfamily, Dorataspida, for the "Acanthometræ cataphractæ," which I considered as the first subfamily of the "Ommatida." That subfamily contained at that time only two genera, Dorataspis (with seven species) and Haliommatidium (with five species). A third genus, Aspidomma (with two species), was united by me with the Haliommatida (because of its double shell). For a fourth genus (Diploconus) with a single species I founded the peculiar family of Diploconida. Therefore the whole number of Acanthophracta described in my Monograph amounted only to four genera and fifteen species. Now the rich collections of the Challenger have added such a great number of new forms, that we may distinguish here thirty-eight genera and two hundred and twelve species.