PLATE XXXIII. 
Gosselettia retusa. 
Page 266. 
Fig. 1. The left side of a well-preserved specimen, showing the general form of the shell. 
Hamilton group. Eighteen Mile creek, Erie Co., N. Y. 
Fig. 2. The antero-eardinal view of the same. 
Mytilarca occidentalis. 
Page 263. 
See Plate 87. 
Fig. 3. A view of the right side of the original of this 1 species. 
Fig. 4. The anterior view of the same. 
Fig. 5. A left valve. The ante-byssal portion is represented as too large. See fig. 11, plate 87. 
Yellow sandstone.' Burlington, Iowa. 
Mytilarca fibristriata. 
Page 264. 
Oa.TSee Plate 87. 
Fig. 6. A left valve. Another figure of this specimen is given on plate 87, fig. 6, to show the form of the 
anterior end and the presence of radii. 
Fig. 7. The right side of the original specimen as seen in a sulphur cast. 
Yellow sandstones. Burlington, Iowa. 
