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



1. Clathrocircus hexaporus, n. sp. 



Sagittal ring circular, smooth, with three pairs of pores (one apical and two basal). The two 

 apical pores are triangular, with two lateral spines, and correspond to the two mitral gates of the 

 Tympanida. The four basal pores form a hexagonal basal plate, with six lateral spines, and 

 correspond to the four basal pores of Semantrum; the two jugular are pear-shaped, and half as 

 broad as the two triangular cardinal pores. 



Dimensions. Height of the sagittal ring 0'08, breadth 0'06. 



Habitat. Cosmopolitan ; Atlantic, Pacific, many Stations, surface. 



2. Clathrocircus octoporus, n. sp. 



Sagittal ring elliptical, smooth, with four pairs of pores (two apical and two basal). The four 

 apical pores are of nearly equal size, subcircular, and form a regular cross around the apical pole. 

 The four basal pores are ovate, and form a quadrangular plate, armed with marginal thorns ; the 

 two jugular pores are somewhat smaller than the two cardinal pores. 



Dimensions. Height of the sagittal ring Oil, breadth 0'08. 



Habitat. Tropical Atlantic, Station 348, depth 2450 fathoms. 



3. Clathrocircus decaporus, n. sp. 



Sagittal ring ovate, thorny, with five pairs of pores (two apical and three basal). The four 

 apical pores are roundish and form a cross. The six basal pores are triangular and form a 

 hexagonal plate with thorny margin ; the two jugular pores are somewhat larger than the two 

 cervical, and half as broad as the two cardinal pores. 



Dimensions. Height of the sagittal ring 0'09, breadth - 07. 



Habitat. North Pacific, Station 256, depth 2950 fathoms. 



4. Clathrocircus stapedius, n. sp. (PI. 92, fig. 8). 



Sagittal ring ovate, smooth, with six pairs of pores (two apical and four basal). The four 

 apical pores are of nearly equal size and form a quadrangular mitral plate with two large lateral 

 horns. The eight basal pores are of very different size (the four central far larger than the two 

 anterior and the two posterior), and form a hexagonal basal plate, also with two large lateral horns. 

 The four branched lateral horns (two upper and two lower) form together an incomplete frontal ring. 



Dimensions. Height of the sagittal ring 01, breadth 0'08. 



Habitat. Central Pacific, Station 271, depth 2425 fathoms. 



