EEPORT ON THE RADIOLARIA. 955 



cardinal second, and the cervical pores thiixl ; but it seems that this succession is 

 often altered, and that the cardinal pores (the largest), appear first, the jugular pores 

 (in front of them) second, and the cervical pores third (or perhaps sometimes in the 

 inverse succession). 



The Cortiniscida, the second subfamily of Semantida, differ from the preceding 

 Semantiscida in the possession of three typical basal feet, which are probably inherited 

 from the Cortinida, and perhaps indirectly from the Plagonida (Plagoniscus). The 

 simplest and the most important form of this second family is Cortiniscus (PI. 92, figs. 

 11—13), differing from its probable ancestral form, Cortina^ in the development of a 

 basal ring, produced by horizontal union of the basal apophyses. The three typical 

 feet are the same as in all triradiate Nassellaeia, two paired pectoral feet {p^, p^) 

 diverging on the anterior base of the sagittal ring, whilst the odd caudal foot (c) lies on 

 its posterior base in the sagittal plane and appears as a basal prolongation of the dorsal 

 rod of the sagittal ring ; the upper part of the dorsal rod is usually prolonged into an 

 ascending apical horn. In Stephaniscus (PL 92, figs. 14, 15) four basal feet are 

 visible, an anterior or sternal foot (z) being added as a prolongation of the basal rod of 

 the ring, opposite to the caudal foot. Finally, Semantiscus (PI. 92, figs. 16—18) is 

 distinguished by the possession of six divergent basal feet, probably identical with those 

 of all six -radiate Nassellaeia ; three of these may be regarded as primary and per- 

 radial, the odd caudal and the paired pectoral feet; the three other intercalated as 

 secondary or interradial feet, the odd sternal (z) and the paired tergal feet {ti, ^u). 



The basal plate of these Cortiniscida exhibits the same important differences as in the 

 preceding Semantiscida, either one, or two, or three pairs of basal gates being developed. 

 But there occur also in some species (mainly in Cortiniscus) only three basal gates, an 

 odd anterior (between the two pectoral feet and a connecting horizontal bar), and two 

 paired posterior (between the two pectoral and the odd caudal foot). It requires further 

 accurate researches to solve the important problem, what the true homologies of these 

 typical basal pores and the separating bars ai'e in the different genera of Semantida. 

 In Semantiscus there are three pairs of basal pores in the horizontal seal, correspond- 

 ing to those of Semantidium, and the radial rods or bai-s between these are the basal parts 

 of the six radial feet ; therefore the odd caudal foot (?) seems to be the posterior, and 

 the odd sternal foot (2) the anterior prolongation of the basal part of the primary 

 sagittal ring; the two paired anterior or pectoral feet (j).^, p ) the prolongations of 

 the coracal rods (e) and the two paired posterior or tergal feet (t^, ?j^), the prolongations 

 of the scapular rods (g). But it is not yet certain whether these six radial feet and 

 the separating gates of the basal plate are all the same and truly homologous in all six- 

 radiate Nassellaeia. In eveiy case the comparative study of the Semantida is of 

 the highest value for the accurate knowledge of the Monopylea, 



