464 THE VOYAGE OF H.M.S. CHALLENGER. 



2. Amphicyclia amphistyla, n. sp. (PL 37, fig. 7). 



Stylocydia amphistyla, Haeokel, 1879, MS. et Atlas (pi. xxxvii. fig. 7). 



Phacoid shell thin walled, two and a half times as broad as the outer and seven times as 

 broad as the inner medullary shell, divided by eighty to ninety radial beams into irregular chambers, 

 which are stratified in four to five floors. Pores regular, circular ; eight to nine on the radius 

 of the phacoid shell, two on the breadth of each chamber. Both marginal spines cylindrical. 



Dimensions. Diameter of the disk (with seven rings) 0'27, of the phacoid shell O'l, outer 

 medullary shell 0'04, inner 0'014. 



Habitat. North Atlantic, Canary Islands, Station 354, surface. 



3. Amphicyclia pachydiscus, n. sp. (PI. 38, fig. 2). 



Phacoid shell very thick, spongy, twice as broad as the outer and five times as broad as 

 the inner medullary shell, divided by fifty to seventy radial beams into subregular chambers, which 

 are stratified in five to six floors. Pores irregular, roundish ; ten to twelve on the radius of the 

 phacoid shell, two to three on the breadth of each chamber. The two opposite marginal spines 

 quadrangular prismatic, very long, as broad as the radius of the inner medullary shell. Fig. '2 

 exhibits a vertical section (slide) through the centre. 



Dimensions. Diameter of the disk (with five rings) 0'22, of the phacoid shell O'l, outer 

 medullary shell - 05, inner 0'02. 



Habitat. South Atlantic, Station 332, depth 2200 fathoms ; fossil in Barbados. 



Genus 200. Trigonocyclia, 1 Haeckel, 1881, Prodromus, p. 458. 



Definition. C occodiscida with three solid radial spines on the margin of the 

 circular disk. Medullary shell simple. 



The genus Trigonocyclia (only known by one single species, once observed) beaivs 

 on the margin of the chambered disk three solid radial spines, at equal distances one 

 from another. It corresponds to the genus Tripodictya amongst the Porodiscida, 



1. Trigonocyclia triangulnris, n. sp. (PL 37, fig. 5). 



Phacoid shell three times as broad as the medullary shell, connected with it by six equidistant 

 radial beams, three of which are prolonged into marginal spines. In the equatorial plane only one 

 single chambered ring, divided by forty-four radial beams into narrow chambers. Pores largo, 

 irregular, roundish ; five on the radius of the phacoid shell, two on each chamber. Surface and 

 margin of the disk spiny. Three strong conical marginal spines, divergent at equal angles, as 

 long as the radius of the disk. 



Dimensions. Diameter of the disk 016, of the phacoid shell 012, of the medullary shell 0'04. 



Habitat. Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen. 



* = Triangular shell with circular rings ; r^r/o-joy, xiixhior. 



