REPORT ON THE RADIOLARIA. 931 



Suborder III. STEPHOIDEA, Haeckel. 



Stephoidea vel Stephida, Haeckel, 1881, Prodromus, p. 444. 

 Acanthodesmida (sensu ampliori), Biitschli, 1882, Zeitschr. f. wiss. Zool., 

 vol. xxxvi. p. 495. 



Definition. NASSELLABIA without complete lattice -shell, with a skeleton composed 

 of one or more simple rings, which may be united by a loose framework and are separated 

 by large openings or gate's. One primary or sagittal ring, determining the sagittal or 

 median plane of the bilateral body, encloses the monaxonian central capsule. 



The suborder Stephoidea, hitherto known by a few species only of " Acantho- 

 desmida," comprises a large number of interesting NASSELLARIA (now more than two 

 hundred species), which possess peculiar interest for the morphology and phylogeny 

 of this legion. The monaxonian central capsule of the Stephoidea is surrounded 

 either by one simple ring or by a complex system of several loosely connected rings ; 

 these may be united by a loose framework of connected branches, but never produce a com- 

 plete lattice-shell, as is constantly the case in the Spyroidea, Botryodea, and 

 Cyrtoidea. Therefore there remain between the parts of the connected rings a few 

 large openings which we call "gates," separating them from the numerous small "pores" 

 of the complete lattice-shells. In the most simple case, if only one ring be formed, 

 there is also present only one " gate," the aperture of this simple ring. 



The first known species of Stephoidea were observed in the Mediterranean by 

 Johannes Miiller in 1856, and described and figured in his last treatise (1858) under 

 the names Lithocircus annularis (loc. cit., Taf. i. fig. 1) and Acanthodesmia vinculata 

 (loc. cit., Taf. i. figs. 47). In the following year I myself observed two other living 

 species in the Mediterranean, and described them in my Monograph (1862, pp. 268, 

 270) as Zygostephanus miilleri (Taf. xii. fig. 2) and Prismatium tripleurum (Taf. iv. 

 fig. 6). For these four longest known Stephoidea I founded the new family 

 of Acanthodesmida (loc. cit., p. 265), but united with them two other similar genera 

 which I afterwards separated : Plagiacantha (belonging to the Plectoidea) and 

 Dictyocha (belonging to the PH^EODAKIA). 



When, in 1876, I received the rich material of the Challenger collection, I was 

 astonished to find in it an enormous number of new, similar, and partly very interest- 

 ing "Acanthodesmida," which were afterwards arranged in my Prodromus (1881, 

 p. 444) in thirty-eight different genera and four " subfamilies," all united in one 

 single large family, " Stephida or Monopylaria cricoidea." I retain here this natural 

 group in the same sense, but give to it the rank of a " suborder," separating at the 

 same time its four subfamilies as substantial " families." Since the names of the 



