1212 THE VOYAGE OF H.M.S. CHALLENGER. 



circular holes, and below the prominent distal end by a broad, triangular, roundish ring of subregular 

 lattice-work (with square pores). Peristome smooth, about half as broad as the thorax 



Dimensions. Cephalis 0'04 long, 0'04 broad; thorax O08 long, 01 broad. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



Subgenus 2. Clathrocorona, Haeckel, 1881, Prodromus, p. 431. 



Definition. Horn of the cephalis fenestrated. Peristome on the margin of the 

 basal mouth with a corona of spines. 



5. Clathrocanium diadema, n. sp. (PL 64, fig. 2). 



Clathrocarona diadema, Haeckel, 1881, Prodromus, p. 431. 



Cephalis hemispherical, thorny, with irregular roundish pores, and a large prismatic horn of twice 

 the length, the three edges of which are denticulate and fenestrated, each with a series of square 

 pores. Length of the two joints = 1:3, breadth = 2:4. Thorax thorny, with three broad fenestrated 

 divergent ribs, which are separated by three large ovate holes (twice as long as the cephalis) and have 

 their prominent distal ends connected below by a broad circular ring of lattice-work (with irregular 

 polygonal small meshes). Peristome wide, two- thirds as broad as the thorax, with a circular 

 corona of small square pores and alternating prominent small teeth. 



Dimensions. Cephalis 0'03 long, 0'04 broad ; thorax 0'07 long, 0'09 broad. 



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



6. Clathrocanium regince, n. sp. (PI. 64, fig. 4). 



Clathrocorona regince, Haeckel, 1881, Prodromus, p. 431. 



Cephalis hemispherical, with irregular roundish pores and a prismatic club-shaped horn of twice 

 the length, the three edges of which are denticulate and fenestrated. Length of the two joints 

 = 1:3, breadth = 1:4. Thorax thorny, with three broad triangular, fenestrated and nodulated 

 ribs, which are separated by three large ovate holes (twice as long as the cephalis) and have their 

 prominent distal ends connected below by a circular ring of lattice-work. Peristome constricted, 

 as broad as the thorax, with a corona of short spines. 



Dimensions. Cephalis 0'03 long, 0'04 broad; thorax 0'08 long, 0'12 broad. 



Habitat. Central Pacific, Station 274, depth 2750 fathoms. 



Genus 541. Lamprodiscus, Ehrenberg, 1860, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, p. 831. 



Definition. S ethopilida (vel Dicyrtida triradiata aperta) with three divergent 

 lateral ribs in the wall of the flat, conical, discoidal, or pyramidal thorax. Cephalis with 

 a horn. Peristome smooth, without corona of spines. 



1 Lamprodiscus = Splendid disk ; 



