1192 THE VOYAGE OF H.M.S. CHALLENGER. 



2. Archicapsa quadriforis, n. sp. 



Shell ovate, rough, a little longer than broad. Pores subregular, circular, twice as broad as the 

 bars. Basal plate with four larger ovate cortinar pores (two smaller jugular and two larger 



cardinal pores). 



Dimensions. Shell 012 to 015 long, 01 to 012 broad. 



Habitat. Central Pacific, Station 265 to 268, depth 2700 to 2900 fathoms. 



3. Archicapsa nonaforis, n. sp. 



Shell pear-shaped, thorny, one and a half times as long as broad. Pores regular, circular, small, 

 hexagonally framed, twice as broad as the bars. Basal plate with nine cortinar pores (three 

 larger alternating with three pairs of smaller pores, as in PL 87, fig. 2). 



Dimensions. Shell 014 long, 0'09 broad. 



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



Section II. DICYETIDA, Haeckel, 1862, Monogr. d. Radiol., pp. 280, 296. 



Definition. Cyrtoidea dithalamia, with two-jointed shell, being divided by a 

 transverse collar stricture into an apical joint (or cephalis) and a basal joint (or thorax). 



Synopsis of the three Families and six Subfamilies of Dicyrtida. 



Family LXIT. ( Mouth open, . -1- Sethopilida. 



Tripocyrtida. 

 Three radial apophyses. ( Mouth closed, . 2. Sethoperida. 



Family LXIII. ( Mouth open, . 3. Sethophormida. 



Anthocyrtida. 

 Numerous radial apophyses. ( Mouth closed, . sthophain 



Family LXFV. ( Mouth open, . -5- Sethocorida. 



Sethocyrtida. 

 No radial apophyses. ( Mouth closed, . 



Family LX1I. TRIPOCYRTIDA, n. fam. 



Sethopilida et Sethoperida, Haeckel, 1881, Prodromus, pp. 431, 433. 



Definition. Dicyrtida triradiata. (Cyrtoidea with a two-jointed shell, 

 divided by a transverse constriction into cephalis and thorax, and bearing three radial 

 apophyses.) 



