1158 



THE VOYAGE OF H.M.S. CHALLENGER. 



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

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

 (genera 511515) and the Haliphonnida (genera 516518) 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 Phsenocalpida, and may be Archicorida which have 

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

 Phsenoscenida (Phcenocalpis, Phcenoscenium) may be derived from the Euscenida 

 (genera 504507) 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 (Calpophcena, 

 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 Phsenocalpida. 



I. Subfamily 



Archiphormida. 

 Basal mouth of the 

 shell a simple wide 

 opening. 



II. Subfamily 



Archiphaenida. 

 Basal mouth closed by 

 a lattice-plate. 



In the axis of the shell-cavity ( Columella sim P le > 



a free columella. 



[ Columella branched, 



Shell-cavity simple, without f A P ex ^ th a horn ' 

 axial columella. {-No apical horn, 



511. Bathropyraims. 



512. Cindopyramis. 



513. Peripyramis. 



514. Litharachnium. 



515. Cladarachnium. 



516. Cyrtophormis. 



517. Haliphorniis. 



518. Arcliiphormiis. 



519. Halicalyptra. 



520. Carpocanistrum. 



521. Arachnocalpis. 



522. Phcenocalpis. 



523. Phcenoscenium. 



524. CalpophcKna. 



525. Archiplicena. 



