PLATE 30. 
Fig. 1 a - e, & 2a- r. Rhynchonella mutabilis 
1 a - e. Ovoid forms of this species. 
2 a, b, c. Profile views of the more gibbous forms, showing the gradual expansion of the 
dorsal valve. 
2 d, e. Front and dorsal views of a very gibbous form. 
2 f—p, and s. Illustrations of extremely gibbous forms, which sometimes present a sub- 
quadrangular outline, and some variation in the form of the broad extension of the mesial 
sinus in front, and in the proportional length and breadth of the dorsal valve as shown in 
2 l and 2 o. The form 2 n is rare, but is nevertheless one which the species sometimes 
assumes. 
2 r. Cardinal view of a cast of this species. 
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