REPOET ON THE RADIOLAEIA. 995 



9. Acrocuhus amphithectus, u. sp. (PI. 93, fig. 17). 



Mitral ring smaller than the basal, both rings elliptical, with curved rods. Four columellse 

 tliorny, also curved, divergent downwards, prolonged upwards into four thorny convergent horns, 

 downwards into four larger branched divergent feet. The two sagittal horns and feet (anterior 

 and posterior) are smaller than the two lateral (right and left) ; therefore the fundamental form 

 of tliis species is distinctly amphithect (as in the Ctcnophora). 



Dimensions. — Breadth of the cube 012 ; total height 0'2. 



Hahitat. — South Pacific, Station 289, depth 2550 fathoms. 



Genus 427. Toxarium,^ n. gen. 



Definition. — T y m p a n i d a with two bisected horizontal rings, connected by four 

 vertical columellee. In the frontal plane two galear bows project upwards, and two 

 thoracal bows downwards. 



The genus Toxarium differs from its ancestral form Acrociibus in the development 

 of two pairs of peculiar bows, placed in the lateral or frontal plane ; the upper pan- 

 projects above the mitral gates, and may be called the " galear bows," the lower pair 

 projects below the basal gates of the cubical shell, and may be called the " thoracal 

 bows." Both pairs are produced originally by the development of two forked vertical 

 spines, arising in the frontal plane on both poles of the priuci25al axis from the sagittal 

 ring (compare Protympanium amphipodium, PL 93, fig. 14). The apical fork- 

 branches become connected ^Adth the lateral corners of the mitral gates, the basal 

 branches with those of the basal gates. By development of lattice-work between the 

 bows and the rings some Spyroidea {Amphispyris, &c.) may have arisen. The 

 important genus Toxarium may be divided into three subgenera. In Toxellium aU 

 the bows are simple, in Toxonium all are forked ; in Toxidium the galear bows are 

 simple, the thoracal bows forked. 



Subgenus 1. Toxellium, Haeckel. 

 Definition. — Galear and thoracal bows simple. , 



1. Toxarium circospyris, n. sp. (PI. 88, fig. 1). 



Galear and thoracal bows simple, of about the same size as the frontal bows between them ; all 

 bows armed with scattered simple conical spines. Sagittal constriction deep, half as long as the 

 whole shell. Lateral outlines of the shell nearly parallel. 



Binicnsions. — Length of the shell 0'16, breadth 0'13. 



Habitat. — Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms. 



' roxa?'i!tjn = Small bow ; 7-o|«g<o«. 



