1194 



THE VOYAGE OF H.M.S. CHALLENGER. 



Synopsis of the Genera of Tripocyrtida. 



a. Three tlio- f -n i v i 



^ " -b set solid, 



A. Three radial 



ribs(orcortinar 

 rods) partly or 

 completely en- 

 closed in the 

 wall of the 

 thorax. Xo 

 latticed vertical 

 cephalic wings. 



L Subfamily 



Sethopilida. 

 Terminal mouth of 

 the thorax a 

 simple wide open- 

 ing. 



IL Subfamily 



Sethoperida. 



Terminal mouth of 

 the thorax closed 

 by a lattice-plate. 



racic ribs pro- 

 longed into 

 three terminal 

 feet. 



h. Three tho- 

 racic ribs pro- 

 longed into 

 three lateral 

 win<;s. 



c. Three tho- 

 racic riljs com- 

 pletely enclosed 

 I in the wall of 

 [ the flat thorax. 



Cephalis I 

 with a horn. \ Feetlatticod, 



Xo horn, feet solid, 



Thorax per- ( -^vjtii hom 

 fectly hit. - 



ticed. ( No horn, . 



Thorax with spongy frame- 

 work. 



Thorax with three large 

 lateral holes between the 

 three ribs, 



Peristome simple, smooth, . 



Peristome with a corona of 

 spines, . 



E. Three radial 

 ribs enclosed 

 in the wall of 

 the thorax and 

 connected with 

 the cephalic 

 horn by three 

 latticed vertical 



C. Three radial 

 beams (or cor- 

 tinar rods) per- 

 fectly free, not 

 enclosed in the 

 wall of the 

 thorax. 



«. Thorax com 

 pletely latticed 



I No frontal horn (four spines), 



1 With frontal horn (five 

 ' spines), . 



b. Thorax witli 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. Ceplialis with 

 a large apical hole. 



D. Three radial terminal feet on \ 

 the [leristome (the three original J- 

 lateral ribs are lost). j 



Thi-ee divergent ribs (or cortinar 

 rods) enclosed either in the 

 wall or in the cavity of the 

 thorax. 



Three divergent free lateral wings 

 (as prolongation of the three 

 ribs) on the sides of the thorax. 



Three free terminal feet (on the 

 base of the thorax). 



Feet solid, . 

 Feet latticed. 



Three ribs enclosed in the 

 lattice-wall of the thorax, 



Three internal rods in the 

 cavity of the thorax. 



Three solid f Cephalis 

 lateral ■) 

 spines. [ ^o ^orn, . 



Throe latticed lateral wings. 

 With horn, 



Three feet solid. 



with horn. 



Three feet 

 latticed. 



Shell with- 

 out exter- 

 nal mantle, 



Shell with an 

 arachnoidal 

 mantle. 



SSi. Dic1yo2jhimus. 



535. Tripocipiis. 



536. SeiJwpi'Hum. 



537. LUhomelissa. 



538. Psilomelissa. 



539. Spoiigomelissa. 



540. Clathrocanium 



541. Lamprodiscus 

 5412. Lampromitra. 



543. Cullhnitya. 



544. Clafliromifrn. 



545. Clafhrocori/a. 



546. Eucecryphalus. 



547. Ampihiplecfft. 



548. Li/c/i II ocan ium. 



549. Lychnodidijum. 



550. Sethopjera. 



551. Litliopera. 



552. Micromelissa. 



553. Peromelissa. 



554. SethomeUssa. 



555. TetraJiedrina. 



556. Setliochyin's. 

 657. Clathrohjclmiis. 



