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



1. Tessaraspis arachnoides, n. sp. (PI. 136, fig. 1). 



Parmal pores pentagonal, ten to twenty times as broad as the thin thread-like bars, on an average 

 of about the same size as the irregular sutural meshes ; the majority of the latter are either 

 triangular or hexagonal. Eadial spines very thin and long, cylindrical, their outer part two to four 

 times as long as the inner. As the insertion of the spines is on the highest point of the plates, the 

 shell becomes polyhedral (dodecahedral ?). 



Dimensions. Diameter of the shell 015 to 017, of the parmal meshes 0'02 to 0'025, sutural 

 meshes O'Ol to 0'03, bars 0'002. 



Habitat. -Equatorial Atlantic, Station 347, surface. 



2. Tessaraspis pentagonalis, n. sp. 



Parmal meshes pentagonal, three to four times as broad as the thick bars, and on an average 

 smaller than the irregular polygonal sutural rneshes. Eadial spines stout, quadrangular ; their outer 

 pyramidal part shorter than the inner prismatic part. 



Dimensions. Diameter of the shell 012, of the parmal pores O'Ol to 0-012, bars 0-003. 



Habitat. Central Pacific, Station 269, surface. 



3. Tessaraspis tetragonalis, n. sp. 



Parmal meshes tetragonal, or nearly square, six to eight times as broad as the thin bars, and 

 on an average larger than the irregular polygonal sutural meshes. Eadial spines thin, quadrangular, 

 prismatic, their outer part longer than their inner. 



Dimensions. Diameter of the shell 016, of the parmal pores 0-012 to 0-016, bars 0'002. 



Habitat. South Pacific, Station 288, surface. 



4. Tessaraspis hexagonalis, n. sp. 



Parmal meshes hexagonal, ten to twelve times as broad as the thin bars, and on an average larger 

 than the polygonal sutural meshes (the two proximal sides of each hexagonal parmal mesh two to 

 three times as long as the four distal sides). Eadial spines cylindrical, thin ; their outer part 

 longer than the inner. 



Dimensions. Diameter of the shell 015, of the parmal pores O'Ol to O'OIS, bars O'OOl. 



Habitat. North Pacific, Station 254, surface. 



5. Tessaraspis trigonalis, n. sp. 



Parmal meshes triangular, three to four times as broad as the thick bars, and on an average 

 smaller than the irregular sutural meshes (in each plate all four parmal meshes of the same size, 

 formed like an isosceles triangle, the distal base of which is somewhat curved, and convex towards 



