I90I S. S. BUCKMAN — BRACHIOPODA 235 



Analogous stage to I. and III. in the Rhynchoncllo', thus : — 



a. Dorsal sulcation slight, 



b. subsequently there is 

 added multiplication. 



Rh. liostraca; Rh. MenegJiinii ; 

 Rh. standis/tetisis, sp. n. 



These are most likely prior stages in the phylogenetic history of 

 many of the fully multiplicate Rhynchonelkc, so that 



b. passes to 



c. multiplication fully de- 

 veloped, continued to 



d. ventral sulcation de- 

 veloped after multipli- 

 cation. 



Rhynch. spp. 



Rhynch. spp. with raised 

 mesial fold. 



Except from W., Rhynchoiiella which attain a similar stage in other 

 ways ; for instance : — 



VI a. Ventral sulcation^ 

 strong ; 

 b. with subsequently de- 

 veloped multiplication. ^ 



Rhynchonclla acuta group. 



VII Striation develops into Rh. fiircillata ; Rh. - rimosa 



multiplication by anas- group ; Rh. Wrighti. 

 tomosis of striae. 



VIII a. Striation alone ; 



b. later a mesial fold de- 

 veloped. 



Rh. diauiriensis, S. Buckm. 

 Rh. dorsetensis, S. Buckm. 



A stage analogous to \a. and \\\a. may have been an early stage 

 in the development of the biplicate Terebratulce. It is found thus : 



I.X. a. Flattened dorsal valve. 



b. Dorsal valve develops 

 gibbosity. 



Terebr. Edwardsi Qnv .) \ 



T. subpimctata (juv.) 



T. Edwardsi ; T. spharoida/is ; 



T. gravida ; T.microtrypa, sp. n. 



