Fig. 1. — Sections across the beak of the pedicle-valves in Syringo- 



thyris and other f/rnrro. (Natural size, except where other- 

 vise stated.) 



CED. (ID. (LP 





a-c—Syringothyris principalis (KJ. 5. 11, and 15 mm. respectively from 

 the apex. 

 d = S. cuspklata mut. exoleta (C), 13 mm. from the apex, at a stage com- 

 parable with (b). [Specimen in the British Museum (Natural 

 History), Geological Department, Reg. B 316.] 

 e = S. elongata (D). Section at a stage comparable with (b). 

 i=S. elongata (C), 10 mm. from the apex, at a stage comparable with (b). 

 [Specimen in the British Museum (Natural History), Geological 

 Department, Keg. B 393.] 

 g—8pvrifer marcyi Hall, after H. S. Williams. 



h = The plate-system in a specimen incorrectly referred to Sp. distans, 

 after Davidson [5] pi. xxxiii, figs. 4 & 5. 

 i-j = Spirifer divplicicosta (D.i), 3 and 6 mm. respectively from the apex ; 

 compare with (a) and (b). 

 k — Sp. distans. with section of the deltidium. 

 \ = Syringospiiri 'prima, after E. M. Kindle. 

 m-n=Tylothyris laminosa (C), 3 and 6 mm. respectively from the apex. 

 o — 8piriferina walcotti. Section 3 mm. from the apex : compare with (c). 

 l J =Pnnctospirifer scabricosta (S),3mm. from the apex: compare with (o). 

 x-t=Cyrtma heteroclita (rX2) ; s-t,the median septum and its partitioned 

 tubs greatly enlarged : s, where completely developed ; t. near its 

 termination. 



