REPORT ON THE RADIOLARIA. 1189 



Cyrtocalpis by development of irregular spongy wickerwork on the surface of the simple 

 lattice-shell ; or from Arachnocalpis (PI. 98, fig. 13) by loss of the peristome. 



1. Spongocyrtis mantis ovis, Dunikowski. 



Spongocyrtis mantis ovis, Duuikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien., vol. xlv. 

 p. 31, Taf. vi. figs. 67, 68. 



Shell broad, ovate, rough, spongy, thick-walled ; length to the breadth = 4:3. Spongy frame- 

 work very dense and dark, with very small roundish pores. Mouth constricted, with a short 

 tubular peristome, about one-third as broad as the shell. 



Dimensions. Shell 0'35 long, 0'26 broad ; mouth 0'08 broad. 



Habitat. Fossil in the Alpine Lias (Schafberg bei Salzburg, Dunikowski). 



2. Spongocyrtis arachnoides, n. sp. 



Shell ellipsoidal, spiny, spongy, thin-walled ; length to the breadth = 3:2. Spongy frame- 

 work loose and delicate, with irregular polygonal meshes and arachnoidal thread-like bars. Mouth 

 constricted, without peristome, about one-fifth as broad as the shell. (Very similar to Arachnocalpis 

 ellipsoides, PI. 98, tig. 13, but without corona around the mouth.) 



Dimensions. Shell 0'32 long, 0'21 broad; mouth 0'04 broad. 



Habitat. Central Pacific, Station 270, depth 2925 fathoms. 



Subfamily 2. AKCHICAPSIDA, Haeckel, 1881, Prodromus, p. 428. 



Definition. C yrtocalpida, with the basal mouth of the shell fenestrated 

 (vel Monocyrtida eradiata clausa). 



Genus 532. Halicapsa, 1 Haeckel, 1881, Prodromus, p. 429. 

 Definition. A rchicapsida with an apical horn. 



The genus Halicapsa, and the following closely allied Archicapsa, represent 

 together the small subfamily of Archicapsida, or of those Cyrtocalpida, in which the 

 basal mouth of the simple shell is closed by a lattice plate. This may be the original 

 state of this family, if it is derived from the Circospyrida (Circospyris, Dictyospyris) 

 by loss of the sagittal constriction and the primary ring. But it is also possible that the 

 Archicapsida have been partly derived from the Archicorida by secondary fenestration 

 of the open mouth. The genus Halicapsa may be easily confounded with the similar 

 Ellipsid Lithapium (compare p. 303, PI. 14, figs. 810). The skeleton of both genera 

 may be perfectly similar, the only distinction being the structure of the central capsule, 

 which in Halicapsa is that of the MONOPYLEA, in Lithapium that of the PERIPYLEA. 



1 Halicapsa = Sea-capsule ; ix;, na^et. 



