Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.
Family LXXII. Cannorrhaphida, Haeckel, 1879 (Pl. [101], figs. 3-14; Pl. [114], figs. 7-13).
Cannorrhaphida, Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 4.
Definition.—Phæodaria with an incomplete skeleton, composed of numerous separate, not radially arranged pieces, which are either hollow tangential spicula or cap-shaped dishes, or fenestrated rings, scattered loosely in the calymma. Central capsule placed in the centre of the spherical calymma.
The family Cannorrhaphida comprises those Phæodaria in which the incomplete skeleton is represented by numerous separate pieces of silica, which exhibit very different forms, and are scattered tangentially on the surface of the spherical calymma, sometimes also throughout its jelly-mass. They agree in this peculiar character with the Thalassosphærida (among the Spumellaria) and bear the same relation to the skeletonless Phæodinida as the Thalassosphærida do to the Thalassicollida (compare pp. [10] and [29]). The Cannorrhaphida represent the former group among the Phæodaria. They differ from the following family, the Aulacanthida, in the arrangement and position of the hollow spicula, which are never directed radially and never touch the central capsule, as is constantly the case in the latter.
Two genera of Cannorrhaphida have been hitherto known. The first species observed in a complete and living state (at Messina in 1859) was Cannobelos cavispicula, described in 1862 in my Monograph as Thalassoplancta cavispicula (loc. cit., p. 261, Taf. iii. figs. 10-13). I there figured a complete living specimen with expanded pseudopodia and a double central capsule (in the stage of self-division). The latter was surrounded by an alveolar calymma and by a voluminous mass of blackish-brown pigment, the phæodium; numerous, long, hollow, cylindrical tubes were scattered on the surface of the calymma. At that time I did not know the tripylean character of the central capsule and the peculiar radiate operculum in the Phæodaria, and therefore placed Thalassoplancta cavispicula among the Thalassosphærida.
The second description of a complete form of Cannorrhaphida was given in 1879 by R. Hertwig, under the name Dictyocha fibula (Organismus d. Radiol., p. 89, Taf. ix. fig. 5). The genus Dictyocha had been already founded by Ehrenberg in 1838, with the following definition:—"Lorica simplex, univalvis, silicea, laxe reticulata aut stellata" (Abhandl. d. k. Akad. d. Wiss. Berlin, 1838, p. 128). Ehrenberg had found only scattered pieces of the skeleton, fossil in Tertiary rocks. He placed them among the Bacillaria (= Diatomaceæ), but added, that they may be possibly scattered spicula of Sponges ("forsan Spongiarum ossicula").
In 1859 I myself observed similar forms of Dictyocha at Messina, and first recognised them as true Radiolaria. But I placed them at that time among the Acanthodesmida, beside Prismatium, supposing that a small spherical body which I had sometimes seen in the cavity of the pileated pieces (probably a phæodellum) was the small central capsule (Monogr. d. Radiol., 1862, p. 271, Taf. xii. figs. 3-6). The complete body of Dictyocha was not described till 1879, when R. Hertwig gave a full description of its peculiar structure, and especially of the great central capsule, which resembles that of the other Phæodaria. He first stated that the singular pileated pieces described by Ehrenberg were not complete shells, but isolated pieces of the skeleton, which are scattered in the jelly-envelope around the central capsule in a mode similar to the spicula of Thalassoplancta, Thalassosphæra and Sphærozoum. Hertwig also first recognised that the thin rods, which compose the reticular pileated pieces of the skeleton in Dictyocha, are not solid bars, but thin hollow tubules, similar to the hollow rods of Aulacantha and of other Phæodaria.
Numerous complete and well-preserved specimens of Dictyocha, which I found in the collection of the Challenger, have convinced me that the accurate description of R. Hertwig is correct in every respect, and that these remarkable bodies are true Phæodaria, most closely allied to Cannobelos (= Thalassoplancta) and to Aulacantha (compare Pl. [101], fig. 10). I now regard them as representatives of a peculiar subfamily of Cannorrhaphida, which I call Dictyochida. To the same subfamily also belong the small annular bodies which Ehrenberg described in 1841 as Mesocena (loc. cit., p. 401), and the elegant, more complicated, reticular and pileated bodies, which Stöhr figured in 1880 under the name Distephanus (Palæontogr., vol. xxvi. p. 121). These peculiar bodies are also only isolated pieces of the siliceous skeleton, and are scattered tangentially in great numbers in the calymma, around the tripylean central capsule. A still higher degree of development is attained by the interesting forms which I describe here as Cannopilus (Pl. [114], figs. 7-13). All these peculiar forms may be derived from the simple annular pieces of skeleton, which are aggregated in great numbers in the calymma of Mesocena. The pieces of the skeleton of these Dictyochida never assume the form of slender, cylindrical, tangential tubules which is characteristic of the Cannobelida.
A third subfamily of Cannorrhaphida, the Catinulida, is represented by the remarkable new genus Catinulus (Pl. [117], fig. 8). The single pieces of the skeleton, scattered in hundreds or thousands throughout the calymma, are here not composed of hollow rods, as in the two former subfamilies, but are solid hemispherical caps, or small, more flatly vaulted dishes, with a peculiar radial striation. All the complete specimens of Catinulus which I could examine possessed four equal central capsules, united in one spherical calymma.