REPORT ON THE RADIOLARIA. 953 



Family XLIX. S e m a n t r d a, u. £am. 



Definition. — S tephoiclea with a single vertical ring (the primary sagittal ring), 

 bearing on its base a horizontal ring (basal or cortiuar ring) with two to four or 

 more basal gates (or cortinar pores). 



The family S e m a n t i d a differs from the preceding Stephanida in the development 

 of a small horizontal ring on the base of the primary vertical sagittal ring. By the 

 crossing of these two rings a small latticed basal plate is formed, with one or two pairs 

 of pores ; rarely with a greater number of " basal pores." The production of this 

 characteristic " basal plate " is of the greatest morphological importance, as the 

 beginning of the numerous different lattice-formations, which are differentiated in the 

 great majority of Nassellaria. 



In my Prodromus (1881, p. 446) I had enumerated the Semantida with three 

 genera (Nos. 298 to 300) as a separate subfamily of the Dyostephida or " Stephoidea 

 bianuularia," and characterised these " Dyostephanida " by the following definition : 

 " Skeleto annulis duobus composito, qui in duobus planis invicem perpendicularibus 

 jacent ; altero annulo (sagittali) verticali, altero (basali) horizoutali." As the names 

 there given were already employed with another signification, and as the Zygostephauida 

 (there united with the Dyostephanida) are more closely related to the Coronida, I 

 now change the names, and propose to call the family Semantida, expressing by this 

 term the typical similarity of the skeleton to a signet-ring (Semantis, Semantrum, 

 Semantidium). 



At about the same time, some Stephoidea of this family were accurately 

 described by Biitschli (1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 495, Taf. xxxii. 

 figs. 6, 7, 8). He called them Ste2:)hanolithis, a name which Ehrenberg had em- 

 ployed, not for complete shells of Eadiolaria, but for isolated parts of such, and for 

 siliceous fragments of different skeletons, needles of Sponges, &e. The three species 

 described by Biitschli represent three different genera of our Semantida, viz., Semantis 

 spinescens (with two gates in the basal plate), Semantrum miilleri (with four gates), 

 and Semantidium haeckelii (with six gates). He pointed out the great morpho- 

 logical value of the fenestrated basal plate and its paired gates, as beginnings of 

 numerous other Nassellakia. But his opinion, that in all S p y r i d e a and C y r- 

 t o i d e a, derived from these, two pau's of basal gates were constant, was erroneous, 

 nor was the formation of the first pair naturally explained ; he supposed that the 

 formation of the basal plate begins by develojament of an odd sagittal apophysis, 

 arising from the base of the primary sagittal ring. But this odd sagittal apoi^hysis 

 (" der unpaare mediane Kieselfortsatz cl", loc. cit., p. 497) is in reality not a primary 



(zool. CHALL. EXP. PART XL. — 18S6.) lir 120 



