996 THE VOYAGE OF H.M.S. CHALLENGER, 



2. Toxarium svbcirculare, n. sp. 



Galear and thoracal bows simple, armed with scattered simple spines, of about equal size, 

 smaller than the smooth frontal bows between them. Sagittal constriction very flat. Therefore 

 the frontal perimeter of the shell is nearly circular. 



Dimensions. Length of the shell 015, breadth 014. 



Habitat. North Atlantic (Antilles), "Weber, surface. 



3. Toxarium thorax, n, sp. (PL 93, fig. 18). 



Galear bows simple, smaller than the frontal bows, and these again smaller than the simple 

 thoracal bows ; therefore the shell increases in breadth towards the base, and resembles the skeleton 

 of the thorax of one of the higher vertebrates (the bow-pairs corresponding to rib-pairs, the ventral 

 part of the sagittal ring to the sternum, the dorsal part to the vertebral column). Sagittal 

 constriction very deep. All bows are armed with scattered, irregularly branched spines. 



Dimensions. Length of the shell 017, breadth 0'2. 



Habitat. Central Pacific, Station 265, depth 2900 fathoms. 



4. Toxarium constrict'um, n. sp, 



Galear and thoracal bows simple, of nearly equal size, larger than the 'frontal bows between 

 them. Therefore the shell is constricted in the equatorial plane. Sagittal constriction also deep. 

 All bows armed with scattered, irregularly branched spines. 



Dimensions. Length of the shell 014, breadth 012. 



Habitat. North Pacific, Station 236, surface. 



Subgenus 2. Toxidium, HaeckeL 

 Definition. Galear bows simple, thoracal bows forked, 



5. Toxarium cordatum, n. sp. (PI. 93, fig. 19). 



Galear bows simple, thoracal bows forked, both somewhat smaller than frontal bows ; all bows 

 armed with scattered simple conical spines, mostly developed at the thoracal bows. Both galear 

 bows are united in a central vertical columella, which arises from the apex of the sagittal ring, and 

 is prolonged into an apical horn. Therefore the sagittal constriction exists only in the basal half of 

 the inversely cordate shell. 



Dimensions. Length of the shell 018, breadth 016. 



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



