PLATE 29. 



Page 

 Fig. I a - o. llUYNCHONELLA SEMIPLICATA. 224 



1 o, b, c. Young individuals which are nearly smooth, or with faint undulations towards the 



front. 

 I d. e. A small individual having the front extremely plicated. 

 1 f- n. Illustrations of the inevailing forms, variety of plications, etc. 

 1 0. Enlargement of the surface, showing the concentric and longitudinal stria>. 



Fig. 2 a - 2, & 3. Rhynchonella .bquivalvis.* 224 



2 a, b, c. Young individuals of this species. 



2 d, e,f & A. Dorsal, ventral, profile, and front views of a larger individual. 



2 t. Enlargement of the concentric strisc. 



3 a, b, c. An individual having a shorter and more rotund form, with a faintly marked .sinus 



in front. This is probably a distinct species. 



Fig. 4 a - o. Rhynchonella mutabilis. 225 



4 o, b, c. Young shells having a more elongate form than the prevailing types. 

 i d -k, and p. The shorter form of this shell in the smaller individuals. 

 4 1-0. Tlie ovoid forms of this species. 



• This species is probably not a true Rhynchonklla : its surfnce-ebaraoters nnd form approach to Rksssei..15RI.*, 

 while in other respects it resembles Khynchospira. 



