PLATE XIII 

 MORPHOGENY OF MAGELLANIINiE (Pages 287-289) 



The figures in the left-hand cohimn, 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 Soacchi ; 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 ro/<ea 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 V>\. — Megerlina Lamarchiana Davidson ; adult form of brach- 

 ial supports. 



Figure E. — Magadiform stage of Magellania; showing completion of 

 descending branches. 



Figure Ei. — Magas pumilus Sowerby, the Cretaceous prototype of 

 this structure. 



Figure F. — MagaselUform. stage ; showing union of descending and 

 ascending branches. 



Figure Fi. — Magasella Cumingi Davidson. 



Figure G. — Terabratdliform 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 terebratellifom stage. 



Figure Hi. — Magellania flavescens Lamarck. 



