1386 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Clathrocydas differs from the preceding closely allied Calocyclas in the 

 dilated mouth and the flatter form of the abdomen, which is usually truncate, conical, or 

 nearly discoidal. The conical thorax is often separated from the flat abdomen by an 

 elegant ribbon of small quadrangular pores. The feet or teeth of the terminal corona are 

 divergent, or even horizontally expanded, whilst in Calocyclas they are usually vertical 

 or somewhat convergent. 



Subgenus 1. Clathrocyclia, Haeckel. 



Defiyiition. — Shell highly conical, often ovate or slenderly campanulate. Cephalis 

 commonly with a single horn. 



1. Clatlii-ocyclas 2^rincipessa, n. sp. (PL 74, fig. 7). 



Shell ovate, with two distinct strictures. Length of the three joints = 1:2:1, breadth = 

 1:2:2. Cephahs hemispherical, large, with a pyramidal, occipital horn of the same length. 

 Thorax subspherical, with irregular, circular pores, about as broad as the bars. Abdomen short, 

 widely open with a single transverse row of circular pores, and a coronal of twelve triangular, 

 divergeiit feet, as long as the abdomen. 



Dimensio7is. — Length of the three joints, a O^OS, h 0'06, c 0'03 ; breadth, a O'Ol:, h O^OS, c 0'09. 



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



2. Clathrocydas basilea, (PL 74, fig. 6). 



Shell campanulate, with two deep strictures. Length of the three joints = 2:5:3, breadth = 

 3:7:9. Cephalis hemispherical, with an ovate, oblique horn of the same length. Thorax hemi- 

 spherical, with subregular, circidar pores of the same breadth as the bars. Abdomen short, with 

 two transverse rows of the same pores, and with a coronal of sixteen to twenty ovate, divergent 

 feet, as long as the horn. 



Dimensions. — Length of the three joints, rt 0-02. h 0-05, c O'Oo ; breadth, a 0-035, b 0-07, c 0-09. 



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



3. Clathrocydas Jtmhriata, Haeckel. 



1 Halicalyptra fimhriata, Ehrenberg, 1875, ALliaudl. d. k. Akad. d. "Wiss. Berlin, p. 72, Taf. ii. 

 fig. 11. 



Shell campanulate, with two deep strictures. Length of the three joints = 1 : 3 : 1, breadth = 

 1:3:5. Cephahs hemispherical, with a conical born of twice tbe length. Thorax hemispherical, in 

 the upper half hyahne, without pores, in the lower half with four to six transverse rows of sub- 

 regular, chcular pores. Abdomen short, suddenly dilated, with one or two transverse rows of larger 



