PLATE XIII 

 MORPHOGENY OF MAGELLANIIN^E (PAGES 287-289) 



The figures in the left-hand column, A-H, represent the stages in the 

 ontogeny of the brachial supports in Magellania, one of the highest 

 genera of the family Terebratellidse. In the right-hand column are 

 shown the adult, permanent, generic structures, corresponding to the 

 stages of Magellania. 



Terebratella passes through all the stages from A to G, Magasella from 

 A to F, and so on, as far as known, for each lower genus. 



All figures are drawn of approximately the same length, to facilitate 

 comparison ; in consequence, the younger stages are much enlarged. 



FIGURE A. Early larval brachiopod, without calcified brachial sup- 

 ports, but with circlet of tentacles on lophophore. The gwyniform stage. 



FIGURE Ai. Gwynia capsula Jeffreys; a morphic equivalent of larval 

 stage, figure A. 



FIGURE B. Later stage of A ; showing growth of septum and con- 

 sequent introversion of edge of lophophore. Cistelliform stage. 



FIGURE Bi. Cistella neapolitana Scacchi ; showing calcification of 

 loop attached to septum, and other adult features. Morphic equivalent 

 of stage B of Magellania. 



FIGURE C. Third stage of Magellania, with small ring on septum. 

 Bouchardiform stage. 



FIGURE Ca. Side view of same. 



FIGURE Ci. Bouchardia rosea Mawe; adult; showing ring on sep- 

 tum as in C. 



FIGURE D. Megerliniform stage of Magellania. 



FIGURE Da. Side view ; showing growth of descending branches as 

 prongs on side of septum. 



FIGURE Di. Megerlina Lamarckiana Davidson; adult form of brach- 

 ial supports. 



FIGURE E. M agadiform stage of Magellania; showing completion of 

 descending branches. 



FIGURE Ei. Magas pumilus Sowerby, the Cretaceous prototype of 

 this structure. 



FIGURE F. Magaselliform stage ; showing union of descending and 

 ascending branches. 



FIGURE Fi. Magasella Cumingi Davidson. 



FIGURE G. Terabratelliform stage ; representing the finished type of 

 structure in Terebratella dorsata Gmelin. 



FIGURE Gi. Terebratella rubicunda Sowerby. Morphically equiva- 

 lent to G, but showing more mature features. 



FIGURE H. Final stage of Magellania venosa Solander, produced by 

 resorption of the septum and connecting bands of the terebratelliform stage. 



FIGURE Hi. Magellania flavescens Lamarck. 



