REPORT ON THE RADIOLARIA. 1365 



length, pear-shaped. Thorax broader than long. Abdomen with three prominent, rounded edges, 

 prolonged over the concave base into three conical, hollow, and fenestrated feet, twice as long as the 

 thorax. Pores small, circular, irregular, in longitudinal series along the edges. 



Dimensions. Length of the three joints, a 0'04, b 0'04, c 012 ; breadth, a 0'04, b 0'06, c 018. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



10. Lithochytris vespertilio, Ehrenberg. 



Litfiochytris vespertilio, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. iv. 

 fig. 10. 



Shell three-sided pyramidal, with two indistinct strictures. Length of the three joints =1:2:5, 

 breadth = 2:3:10. Cephalis with a short horn of half the length, conical. Thorax inflated. 

 Abdomen without prominent edges, divided in the lower half into three large, conical, hollow, and 

 fenestrated feet, twice as long as the thorax. Pores small, irregular, roundish. 



Dimensions. Length of the three joints, a 0'02, b 0'04, c 01 ; breadth, a 0'04, b 0'06, c 0'2. 



Habitat. Fossil in Barbados. 



Family LXVI. PHORMOCYRTIDA, n. fam. 



Theophormida et Theoplicenida, Haeckel, 1881, Prodromus, pp. 436, 437. 



Definition. Tricyrtida multiradiata. (Cyrtoidea with a three-jointed 

 shell, divided by two transverse constrictions into cephalis, thorax, and abdomen, with 

 numerous, four to nine or more, radial apophyses.) 



The family Phormocyrtida, composed of the Theophormida and Theophsenida 

 of my Prodromus, comprises those Cyrtoidea in which the lattice-shell is three- 

 jointed, and bears numerous radial appendages (usually six or nine, sometimes more, 

 rarely less, four or five). The two subfamilies differ in the shape of the terminal mouth, 

 which is in the Theophormida a simple wide opening, in the Theophsenida closed by a 

 lattice-plate. The phylogenetic origin of the Phormocyrtida may be found either in the 

 Podocyrtida or in the Anthocyrtida ; they may be derived either from the former by 

 interpolation of interradial, secondary apophyses between the three primary perradial 

 apophyses ; or from the latter by development of an abdomen. 



The radial apophyses are originally radial ribs, which arise from the base of the 

 cephalis on the collar stricture, run along the thorax and abdomen, and are often pro- 

 longed into terminal feet. Whilst in some forms the radial ribs are completely 

 preserved in both joints, they are in other forms only partly visible (in the abdomen), 

 and very often only their free terminal prolongations are preserved in the form of a corona 

 of feet around the mouth of the thorax. This corona is either simple or double. Some- 

 times also a corona is developed on the lumbar stricture, between the thorax and abdomen. 



