REPORT ON THE RADIOLARIA. 1261 



1. Spongopyramis spongiosa, n. sp. (PL 56, fig. 10). 



Plectopyramis spongiosa, Haeckel, 1881, Prodromiis et Atlas, loe. cit. 



Shell partly or entirely enveloped by spongy framework, slender, pyramidal, with rather straight 

 outlines. CephaUs very small, ovate, hyaline. Thorax with nine very stout and nearly straight 

 ribs, which are connected by fifteen to twenty or more irregular, interrupted transverse bars. The 

 irregular quadrangular meslies so produced are filled up by an irregidar secondary network, with 

 meshes of very different size and form. The dense spongy envelope, which in the specimen figured 

 covered only half the shell, was complete in another older specimen. 



DiTnensions. — Cephalis 0'015 long, O'Ol broad; thorax 0"4 long, 0'25 broad. 



Habitat. — Central Pacific, Station 271, depth 2425 fathoms. 



2. Spongopyramis spongoplecta, n. sp. 



Shell entirely enveloped by spongy framework, pyramidal, with straight outlines. Cephalis 

 ovate (twice as large as in the preceding species), with small circular pores. Thorax with twelve 

 stout and straight ribs, which are connected by twenty to twenty-five annular, transverse bars. 

 The subregular square meshes so produced are filled up by irregular, spongy network, which 

 envelops the whole shell more loosely than in Spongopyramis spongiosa. 



Dimensions. — Cephalis 0'03 long, 0'02 broad ; thorax O'o long, 0'2 broad. 



Habitat. — Central Pacific, Station 272, depth 2600 fathoms. 



Genus 563. Acanthocorys,^ Haeckel, 1881, Prodromus, p. 432. 



Definition. — S etliophormicla (vel Dicyrtida multiradiata aperta) vs^ith numerous 

 radial ribs in the wall of the pyramidal thorax, prolonged into divergent terminal feet. 

 Network simple. Cephalis commonly with several horns. 



The genus Acanthocorys and the following nearly allied Arachnocorys possess a near 

 relation to the three preceding pyramidal genera, but differ from them in the terminal pro- 

 longation of the radial ribs, which are commonly spiny and form a corona of free feet 

 around the mouth of the thorax. The cephalis is usually much larger than in the three 

 preceding genera, and bears a variable number of radial horns. Therefore these two genera 

 are probably older and nearer to the common ancestral form of the Sethophormida 

 than the preceding genera. It may be derived directly from Bictyophimus by inter- 

 polation of three secondary (interradial) ribs between the three primary (perradial) ribs. 



1 Acanthocorys = S^my helmet ; xxxudec, k6(vs. 



