1268 THE VOYAGE OF H.M.S. CHALLENGER. 



Arachnocorys araneosa (Tl. 56, fig. 11), but differing in the structure of the eephalis, and in the greater 

 number of the ribs and spines. 



Dimensions. — Cephalis 0-04 diameter, thorax 012 long, 0-24 broad. 



Habitat. — South Pacific, Station 300, depth 1375 fathoms. 



Genus 5G5. Anthocyrtoma,^ n. gen. 



Definition. — S e t h o p h o r m i d a (vel Dicyrtida multiradiata aperta) without thoracic 

 ribs, with six terminal feet around the mouth. Cephalis free, with an apical horn. 



The genus Anthocyrtoma and the four following genera form together the peculiar 

 group of Carpocanida, comprising all those Sethophormida in which the original thoracic 

 ribs are lost, and only the terminal feet remain. Anthocyrtoma is the simplest form 

 of this group, possessing only six terminal feet, three primary perradial, and three alter- 

 nating, secondary, interradial. It may be directly derived either from Lychnocanium, 

 by interpolation of three interradial feet, or from Hexasj^yris by loss of the sagittal 

 ring. 



I. Anthocyrtoma senmlata, Haeckel. 



Anthocyrtis serrulata, Ehrenberg, 1875, Abhandl d. k. Akad. d. Wiss. Berhn, p. 66, Taf. vi. 

 fig. 7. 



Shell pear-shaped, rough, with obliterated collar stricture. Length of the two joints =1 : 4, 

 breadth = 1 : 3. Cephalis ovate, with very small pores, and a stout conical horn of the same 

 length. Abdomen inflated, truncate, with larger, regular, circular pores, twice as broad as the con- 

 stricted mouth. Six feet vertical, parallel, serrate, all of the same size, about as long as the 

 cephalis. 



Dimensions.- — Cephalis 0"06 long, O'Oo broad; thorax 0'2 long, 017 broad. 



Habitat — Fossil in Barbados. 



2. Anthocyrtoma alterna, n. sp. 



Shell pear-shaped, smooth, with distinct collar stricture. Length of the two joints = 1:5, 

 breadth=l:6. Cephalis hemispherical, with a slender conical horn of twice the length. 

 Abdomen inflated, subglobular, with regular, circular, hexagonally framed pores, three times as broad 

 as the narrow, constricted mouth. Six feet conical, smooth, somewhat divergent, alternating, of 

 different sizes ; the three larger (perradial) half as long as the shell, and twice as long as the three 

 smaller (interradial). (Similar to Antlwcyrtis ventricosa.) 



Dimensions. — Cephalis 0'03 long, 0-04 broad ; thorax 015 long, 018 Ijroad. ^ 



Hahitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms. 



' .4?ifAoci/rt077ia= Flower-arch ; sivh;, nii^ujiix. 



