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Fig. 1 a - p. Rhynchonella yellicata. 230 
1 a - e. Dorsal, ventral, and profile views of characteristic specimens. 
1 /, g. A form more rotund than usual. 
1 h. An individual with a strongly marked sinus and much elevated mesial lobe. 
1 i. Profile view of a gibbous form. 
1 fc, l, m, ii. More gibbous forms, which may probably be a variety of R. abrupta. 
1 o. Enlargement of the plications in front, showing the central impressed lines and arching 
strim. 
1 p. Cast of the ventral valve, showing thelobed muscular impression. 
Fig. 2 a - k . Rhynchonella altiplicata. 231 
2 a. b. Dorsal views of two small individuals. 
2 c, d. Front views of the same. 
2 e. Profile of one of these. 
2/, g. Dorsal and ventral views of a larger individual. 
2 h, i. Front and profile of the same. 
2 fc. Enlargement of the surface, showing the angular plications and sharply arching striae, 
which are more closely arranged than represented in the figure. 
Fig. 3 a - e . Rhynchonella acutiplicata. 232 
3 a, b. Dorsal and ventral views of a specimen of this species. 
3 c, d. Profile and front views of the same. 
3 e ( by mistake 3d). Enlargement of the plications and concentric striae 
