PLATE 33. 



rage 



Fig. 1 a - p. Rhtnchonella vellicata. 230 



1 a - e. Dorsal, ventral, and profile views of cliaracteristic specimens. 

 lf,g. A form more rotund than usual. 



1 h. An individual with a strongly marked sinus and much elevated mesial lobe. 

 1 t. Profile view of a gibbous form. 



1 k, I, m, n. 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 



striae. 

 1 p. Cast of the ventral valve, showing the lobed muscular impression. 



Fig. 2 a - A-. Rhtnchonella altiplicata. 2.S1 



2 o, 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 A, I. Front and profile of the same. 



2 fc. Enlargement of the surface, showing the angular plications and sharply arching stria!, 

 which are more closely arranged than represented in the figure. 



Fig. 3 a - e. Rhtnchonella acutiplioata. 232 



3 o, 6. 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. 



