1072 THE VOYAGE OF H.M.S. CHALLENGER. 



Subfamily 8. CIRCOSPYRIDA, Haeckel, 1881, Prodromus, p. 443. 

 Definition. Z ygospyrida apoda, without descending basal feet. 



Genus 467. Circospyris, 1 Haeckel, 1881, Prodromus, p. 444. 

 Definition. Z ygospyrida without basal feet, with an apical horn. 



The genus Circospyris and the following closely allied genus Dictyospyris 

 represent together the small subfamily Circospyrida, differing from all other Zygospyrida 

 in the absence of feet on the basal face. They have probably arisen from the Tripos- 

 pyrida (Tripospyris) by reduction and loss of the feet (in the same way as the 

 eradiate Cyrtoidea from the triradiate). But it is also possible that many of the 

 Circospyrida (if not all) are derived directly from the Semantida (Clathrocircus) by 

 the closing of the two lateral. openings and by completing the framework. 



1. Circospyris nucula, n. sp. (PL 95, fig. 13). 



Shell nut-shaped, compressed, smooth, with prominent sagittal ring. On each side of the ring 

 three to four pairs of very large annular polygonal pores. Lateral pores small and numerous, 

 roundish. Basal plate with two large pores only. Horn slender, conical, shorter than half the shell. 



Dimensions. Shell (Ml long, CMS broad. 



Habitat. Tropical Atlantic, Station 347, depth 2250 fathoms. 



2. Circospyris gigas, Haeckel. 



Dictyospyris gigas, Ehrenberg, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xix. fig. 6. 



Shell nut-shaped, tuberculate, with distinct sagittal stricture. On each side of the ring four 

 pairs of larger annular pores. Lateral pores roundish, smaller. Basal plate with four large 

 central and a circle of eight to twelve smaller peripheral pores. Horn cylindrical, about half as 

 long as the shell (in the inverted figure of Ehrenberg directed downwards). 



Dimensions. Shell 01 to 015 long, 015 to 0'2 broad; horn 0'05 to 0'08 long. 



Habitat. Fossil in Barbados. 



3. Circospyris tridentata, Haeckel. 



Dictyospyris tridentata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xix. 

 fig. 10, a, b. 



Shell nut-shaped, smooth, with sharp sagittal stricture. On each side of the ring two pairs of 

 large annular pores. Lateral pores roundish, smaller. Basal plate with six large pores. Horn 

 slender, cylindrical, about as long as the shell, with three sharp teeth at the distal end. 



Dimensions. Shell 0'03 long, 0'05 broad ; horn 0'03 long. 



Habitat. Fossil in Barbados. 



1 Cvrcoepyris = Basket with a ring ; 



