1158 



THE VOYAGE OF H.M.S. CHALLENGER. 



The Phainocalpida are probably an artificial family, composed of three or four (or 

 perhaps more) different groups, which have a quite difi"erent origin. The Litharachnida 

 (genera 511-515) and the Haliphormida (genera 516-518) are probably derived from 

 the Sethophormida by loss of the cephalis, the retrograde metamorphosis of which 

 may be observed in all its different stages. The Halicalyptrida (genera 519-521) are 

 perhaps independent of the other Phaenocalpida, and may be Archicorida which have 

 produced a corona of teeth around the mouth, without relation to lost radial ribs. The 

 Phaenoscenida {Phcenocaliyis, Phcenoscenium) may be derived from the Euscenida 

 (genera 504-507) by interpolation of interradial feet between the three primary ones, or 

 directly from the P 1 e c t o i d e a. The Calpophsenida, on the other hand {GalpophcBna, 

 Archiphcena), may have arisen from the Zygospyrida (Petalospyris, Gorgospyris) by 

 loss of the sagittal ring and the longitudinal constriction. The phylogeny of the 

 Phsenocalpida is therefore a very complicated problem, as yet unsolved. 



Synopsis of the Genera of Phamocalpida. 



1. vSubfamily 



Archiphormida. 

 Basal mouth of the 

 shell a simple wide 

 opening. 



Radial ribs 

 enclosed in 

 the wall of 

 the shell, 

 usually pro- 

 longed into 

 free terminal 

 feet. 



II. Subfamily 



Archiphsenida. 

 Basal mouth closed by " 

 a lattice-plate. 



Shell slender, 



pyramidal 

 (without horn). 



Shell flatly 

 campanulate or 

 discoidal (with- 

 out horn). 



' Shellsimple,withsimplenet- 

 work, 



Shell simple, with double 

 network. 



Shell double, with an outer 

 mantle, . 



Radial ribs simple, . 

 Radial ribs branched, 



Mouth smooth, constricted 

 Shell ovate, i^o horn), 



urceolateor ^ Mouth with (With horn, 

 campanulate. ^ ^^^^^^ ^^ j 



feet. ( No horn, 



' Shell simple ( With horn, . 

 without ■; 

 mantle. ( No horn, . 



Shell double, with an exter- 

 nal mantle (no horn). 



Columella simple, . 



Columella branched, 



No radial ribs in the wall of 

 the shell. Mouth surround- 

 ed by a corona of free ter- 

 minal feet. 



In the axis of the shell-cavity 

 a free columella. 



Shell-cavity simple, without ) ' ' 



axial columella. ^ j^^ ^^-^^^ j^^^^^ 



511. Bathropyramis. 



512. Cindopyramls. 



513. Peripyramis. 



514. Litharachnium. 



515. Cladarachniuvi. 



516. Cyrtoph ormis. 



517. HaUphormis. 



518. Archiphormis. 



519. Halkalyptra. 



520. Cmpocanistrum. 



521. Arachnocalpis. 



522. Phcenocalpis. 



523. Phcenoscenium. 



524. GalpophcBna. 



525. ArcliixiluBna. 



