REPORT ON THE RADIOLARIA. 659 



opposite in pairs in two crossed diagonal planes. Inner cortical shell of the same shape, but 

 two-thirds smaller, also thorny. Transverse girdle broad, with four pores on the isthmus. (This 

 species appears to be the common Tetrapyle octacantha, with doubled cortical shell.) 



Dimensions. Length of the first shell 0'04, breadth 0'03 ; length of the second shell 016, 

 breadth 012 ; length of the third shell 0'24, breadth 018. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



5. Tetrapylonium armatum, n. sp. 



Outer cortical shell nearly quadrangular, one and a fourth times as long as broad, with 

 very spiny surface. Between numerous smaller (simple or branched) thorns arise twelve larger 

 radial spines, symmetrically distributed, eight wing-spines crossed in two diagonal planes (as in 

 Tetrapylonium octacanthum) and four corner spines on the four rounded corners of the lateral 

 plane (as in Tetrapylonium quadrangulare). Therefore this species combines the armature of both 

 foregoing species. Four gates kidney-shaped. Inner cortical shell elliptical, smooth, three- 

 fourths smaller. 



Dimensions. Length of the first shell 0'045, breadth 0'035 ; length of the second shell 018, 

 breadth 015 ; length of the third shell 0'25, breadth 0'2. 



Habitat. Pacific, central area, Station 266, depth 2750 fathoms. 



Genus 288. Pylozonium, 1 n. gen. 



Definition. P y 1 o n i d a with trizonal lentelliptical medullary shell, surrounded by 

 double latticed cortical shell ; inner cortical shell as well as the outer Pylonium-shaped, 

 each with three perfect crossed girdles (transverse, lateral, and sagittal). 



The genus Pylozonium is the most highly developed form of the Pylonida, as all 

 three systems of concentric girdles here become fully developed, each system with three 

 perfect girdles. In this genus only among all the Pylonida we find nine complete 

 latticed girdles, and in each of the three dimensive planes three concentric elliptical 

 girdles. The first system forms the medullary shell, the second system the inner cortical 

 shell, and the third system the outer cortical shell. 



1. Pylozonium novemcinctum, n. sp. 



Outer cortical shell lentelliptical, thorny, one and a third times as long as broad, without radial 

 spines, with four kidney-shaped gates. Inner cortical shell of the same shape, but one-third 

 smaller, four times as large as the lentelliptical medullary shell. 



Dimensions. Length of the medullary shell 0'04, breadth 0'03 ; length of the inner cortical 

 shell 016, breadth 012 ; length of the outer cortical shell 0'24, breadth 018. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



1 Pylozonium = Shell with gates and girdles ; *-iix>j, Bunion. 



