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 'J'erebratellithc. In the right-hand column are 

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

 stages of Ma(/eUania. 



TerebratelUi passes tln-ough 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 lengtli, to facilitate 

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



Fi(iURE A. — Early larval brachiopod, without calcified brachial sup- 

 ports, but with circlet of tentacles on lophophore. Tlie (jwynijorm stage. 



Figure Ai. — Gwynia capsula Jeffreys; a morphic e(|uivalent of larval 

 stage, figure A. 



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

 sequent introversion of edge of lopliophore. Cistelliform stage. 



Figure Bi. — Cistella neajmlitana Scacchi ; showing calcification of 

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

 of stage B of Mucjcllania. 



Fkutre C. — Third stage of Magdliviia, with small ring on septum. 

 Bouchdrdiforrn stage. 



Figure Ca. — Side view of same. 



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

 tum as in C. 



Figure D. — MegerUniform stage of Magellantn. 



Figure D«. — Side view ; showing growth of descending brandies as 

 prongs on side of septum. 



Figure Di. — MegerUna Lamarctmna Davidson ; adult form of brach- 

 ial supports. 



Figure E. — Magadiform stage oi Magellaiiia ; 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. — Magnsclla Cumingi Davidson. 



Figure (i. — TtrahrntrUiform stage; representing the finished type of 

 structure in Terehratidla dormla Gmelin. 



FifiURE Gi. — Terebrafella ruhicunda Sowerby. Morphically equiva- 

 lent to G, but showing more mature f(>atures. 



Figure H. — Final stage of Mngplldnui venoan Solander, produced by 

 resorption of the septum and connecting bauds of the terehratelliform stage. 



Figure Hi. — Magellania Jlavescens Lamarck. 



