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



are aspinal pores (two at the base of each spine), the others sutural pores. All pores nearly of 

 the same size. As the shell of this species is very dark and thick-walled, it was impossible to 

 obtain more information with regard to the pores. Eadial spines very stout ; the outer conical 

 part shorter than the inner cylindrical part. 



Dimensions. — Diameter of the shell 0"2, of the pores 0'006 to O'OOS. 



Habitat. — ISTorth Pacific, Station 236, surface. 



Genus 355. Hystricliaspis,^ n. gen. 



Definition. — Do rat asp id a with twenty plates, which are perforated by forty 

 aspinal pores (two pores in each plate). Surface of the shell with numerous dimples, 

 separated by a network of elevated combs. Numerous by-spines. 



The genus Hystvichaapis has the same structure with regard to the shell, as its 

 ancestral form Ceriaspis, and differs from the latter only in possessing numerous by- 

 spines. Moreover, in the former the dimples of the shell-surface are either all 

 perforated by pores, or some of them are blind. 



Subgenus 1. Hystvichasparium, Haeckel. 



Definition.- — Shell with seventy to one hundred or more funnel-shaped dimples, 

 •Bach of which opens on the bottom by one aperture or liy a couple of pores ; 

 twenty larger dimples in the centre of the plates (each with a couple of pores, some- 

 times also three couples) and fifty to one hundred or more smaller dimples, each of 

 which contains one sutural pore. No blind dimples between the perforated dimples. 



1. Hystrichaspis 2)ectinata, n. sp. (PI. 138, fig. 8). 



Shell with numerous (one bundled to two hundred?) funnel-shaped dimples, each of which is 

 pierced at the bottom by one or two pores ; twenty larger dimples in tlie centre of the plates (eacli 

 with two aspinal pores), and fifty to one hundred and fifty or more smaller dimples (each with one 

 sutural pore). No blind dimples. Crests between the dimples armed with a continuous series of 

 simple by-spines. Eadial main spines stout, in the inner lialf cylindrical, in the outer conical, more 

 or less compressed. 



Dimensions. — Diameter of the shell 0'13, of the pores 0'004 to O'OOIi. 



Habitat. — Tropical Atlantic, Station 352, surface. 



2. Hystrichaspis furcata, n. sp. (PI. 138, fig. 9). 



Shell with numerous (one hundred to two hundred ?) funnel-shaped dimples, each of which is 

 pierced at the bottom by one or two pores ; twenty larger dimples in the centre of the plates (each 



1 JT?/s/ru7i((sj)is= Porcupine-shield ; var^ti,, aairi;. 



