REPORT ON THE RADIOLARIA. 803 



stock of this whole order, with the exception of the Sphserocapsida. The four following 

 families of the order may be easily derived from the Dorataspida. The number of 

 genera (seventeen) and of species (one hundred and eight) is in this family greater than 

 in the other five families together. When I constituted that family in my Monograph 

 1862, it comprised only one genus, Dorataspis, with seven species. The nearly allied 

 genus Haliommatidium (Phatnaspis) belongs to the Belonaspida. 



The Dorataspida differ from the other Ac an th o ph r act a in the simple 

 spherical lattice -shell, which is composed of the meeting apophyses of the twenty 

 radial spines. In three other families of the suborder the shell is not spherical, but 

 ellipsoidal (Belonaspida), discoidal (Hexalaspida), or diploconical (Diplocoiiida). In the 

 Phractopeltida the spherical shell is double, composed of two concentric lattice-spheres. 

 In the Sphserocapsida the simple spherical shell is not composed of the apophyses of 

 the spines, but of innumerable small plates. 



The family Dorataspida may be divided into two very different subfamilies, which 

 are probably derived, independently of one another, from two different subfamilies of 

 the Astrolonchida. The first subfamily, Diporaspida, exhibits on each radial spine two 

 opposite apophyses, like its ancestral group, the Phractacanthida (p. 753) ; whereas 

 the second subfamily, Tessaraspida, possesses on each radial spine four crossed 

 apophyses (opposite in pairs), like its ancestral group, the Stauracanthida (p. 758). 

 Therefore the composition of the spherical shell, produced by the meeting branches of the 

 tangential apophyses, is essentially different in the two subfamilies : in the Diporaspida 

 each radial spine is surrounded by two opposite primary aspinal meshes, in the 

 Tessaraspida by four crossed primary aspinal meshes. 



Another principle of division may be established for the whole family by the different 

 mode of composition of the shell, and regarding this important difference we may distin- 

 guish also two different subfamilies as C 1 a d o p h r a c t a and Peltophracta. In 

 the first and simpler subfamily, the C 1 a d o p h r a c t a, the shell is composed totally (or 

 sometimes partially) of the meeting branches of the apophyses of the neighbouring spines ; 

 but in each single spine (or in the most part of them) the branches of the apophyses are 

 not united, and form no lattice-plate (PI. 137, figs. 1 to 8). Whereas in the Pelto- 

 phracta the shell is composed constantly of twenty perforated plates, as in each 

 single spine the branches of its apophyses are united and form a fenestrated shield with 

 two or four (and sometimes numerous) pores (Pis. 135, 136, 138). 



In the Diporaspida as well as in the Tessaraspida we find numerous representatives 

 of the two groups of the Cladophracta and of the Peltophracta; therefore 

 the whole family of Dorataspida may be divided into four different tribes. The 

 Diporaspida (with two opposite apophyses on each spine) are partly Cladophracta 

 (the Phractaspida, PI. 137, figs. 1-4), partly Peltophracta (the Ceriaspida, 

 PI. 138). On the other hand the Tessaraspida (with four crossed apophyses on each 



