KEPORT ON THE RADIOLARIA. 



851 



aspinal pores, and two, four, or more (secondary) coronal pores. In the majority of 

 species the two opposite apophyses are first crossed at right angles by a trans- 

 verse beam, and the two parallel transverse beams are again crossed by perpendicular 

 tertiary branches (again parallel to the apophyses). ' In this case the network of the 

 free lattice-plates becomes more or less rectangular. But in other species the 

 ramification of the apophyses assumes more the form of bifurcation or of irregular 

 branching. As already said, the neighbouring free lattice-plates of this third order 

 never meet, and therefore a complete third shell is never formed. 



The different genera of Phractopeltida exhibit very remarkable differences in the 

 development of free apophyses (or lattice-plates of the third order). Whilst in the 

 numerous species of the ancestral genus Phractopelta all twenty spines remain simple, 

 without such apophyses, only in a single observed species (representing the genus 

 Pantopeltci) were all twenty spines protected by them. In the three other genera 

 only one part of the spines bears free apophyses, but not the other part. The most 

 frequent form is Dorypelta (PI. 133, fig. 2) ; here eight spines are simple (four 

 equatorial and four polar spines of the hyclrotomical plane), whilst twelve spines bear 

 apophyses (eight tropical and four polar spines of the geotomical plane). In 

 Octopelta the eight tropical spines only bear apophyses, whilst the twelve other 

 (four equatorial and eight polar) are simple. In Stauropelta finally the four equatorial 

 spines only are simple, whilst the sixteen others bear free apophyses (eight tropical and 

 eight polar spines). 



The Central Capsule of the Phractopeltida is constantly spherical, and enclosed 

 between the two concentric spherical shells ; it is therefore larger than the inner and 

 smaller than the outer shell. Its wall is pierced by the twenty radial beams connecting 

 the two shells. The shape of the central capsule and of the enveloping calymma is the 

 same as in the other A c a n t h o p h r a c t a and specially in the Dorataspida. 



Synopsis of the Genera of Phractopeltida. 



\ All twenty spines without apophyses in the free 



All twenty spines of the same form, 



external part, 



366. Phmdopelti'. 



[ All twenty spines with apophyses in the free part, 367. Pant<i)>rlla. 



Eight tropical spines with apophyses, twelve 



others (eight polar and four equatorial) simple, 368. Odo^ clfii. 



Twenty radial spines, partly without, 

 paitly with apophysi-s in the free - 

 external part, 



Twelve radial spines (eight tropical and four 

 polar) with apophyses, eight others (four polar 

 and four equatorial) simple, . . 3(59. l)n, // 



Sixteen radial spines (eight tropical and eight 



polar) with apophyses, four equatorial, simple, 370. Sta'irope'ta. 



