1194 



THE VOYAGE OF H.M.S. CHALLENGER. 



Synopsis of the Genera of Tripocyrtida. 



a. Three tho- [" 



racic ribs pro- Cephalis f * 



longed into J *& a horn. ( j- ee 

 three terminal | 



feet. ^ horn, feet solid, 



A. Three radial 

 ribs(orcortinar 

 rods) partly or 

 completely en- 

 closed in the 

 wall of the 

 thorax. No 

 latticed vertical 

 cephalic wings. 



I. Subfamily 



Sethopilida. 

 Terminal mouth of 

 the thorax a j 

 simple wide open- 

 ing. 



Feet solid, . 

 Feetlatticed, 



b. Three tho- 

 racic ribs pro- 

 longed into 

 three lateral 

 wings. 



Thorax per- I With ho 

 fectly lat- { 



ticed. ( No horn, . 



Thorax with spongy frame- 

 work, 



Thorax with three large 

 lateral holes between the 

 three ribs, 



c. Three tho- \ 

 racic ribs com- Peristome simple, smooth, . 



pletely enclosed^ p er i s tome with a corona of 

 m the wall of g iueS) _ 



the flat thorax. [ 



B. Three radial 

 ribs enclosed 



in the wall of 



the thorax and 



connected with - 



the cephalic 



horn by three 



latticed vertical 



wings. 



C. Three radial 

 beams (or cor- 

 tinar rods) per- 

 fectly free, not 

 enclosed in the 



wall of the 

 thorax. 



D. Three radial terminal feet on j jr ee so ii(j ; 

 the peristome (the three original > 



lateral ribs are lost). j Feetlatticed, 



l No frontal horn (fourspines), 



a. 1 borax com- ) 



pletely latticed. 1 Witl1 frontal horn (five 



I spines), . 



b. Thorax with three large lateral holes between 

 the three ribs. No frontal horn, . 



Three beams outside the thorax, arising freely 

 from the collar stricture (no cephalic hole), 



Three beams inside the thorax. Cephalis with 

 a large apical hole, 



Three divergent ribs (or cortinar 

 rods) enclosed either in the 

 wall or in the cavity of the 

 thorax. 



Three ribs enclosed in the 

 lattice-wall of the thorax, 



Three internal rods in the 

 cavity of the thorax, 



II. Subfamily 



Sethoperida. 



Terminal mouth of ( 

 the thorax closed | 

 by a lattice-plate. | 



Three divergent free lateral wings 

 (as prolongation of the three < 

 ribs) on the sides of the thorax. 



( Cephalis 

 with horn, 



wingg _ 



Three free terminal feet (on the 

 base of the thorax). 



Three solid 

 lateral \ 

 spines. [ 



| Three latticed 

 [ With horn, 



[ Three feet solid, 



Shell with- 

 out exter- 

 nal mantle, 



Shell with an 

 arachnoidal 

 . mantle, 



Three feet 

 latticed. 



534. DictyopTiimus. 



535. Tripocyrtis. 



536. Sethopilium. 



537. Lithomelissa. 



538. Psilomelissa. 



539. Spongomelissa. 



540. Clathrocaniuin 



541. Lamprodiscus 



542. Lamprornitra. 



543. Callimitra. 



544. Clathromitra. 



545. Clatkrocorys. 



546. Eucecryphalun. 



547. Amphiplecta. 



548. Lychnocanium. 

 649. Lychnodidyum. 



550. Sethopera. 



551. Lithopera. 



552. Micromelissa. 

 5i>3. Peromelissa. 



554. Sethomelissa. 



555. Tetrahedrina. 



556. Sethochytris. 



557. Clatlirolychnus, 



