EXPLANATION OF PLATES. 
PLATE 1. 
Figure 1. Cranium of the type of Sibbaldius tectirostris Cope. Dorsal view. Philadelphia Academy of 
Natural Sciences. 
FIGURE 2. Cranium of Balcenoptera physalus (L.). Dorsal view. No. 16045, U. S. National Museum. Cape 
Cod, Mass. Collected by the U.S. Fish Commission. 
FIGURE 3. Cranium of Balenoptera physalus (L.). Dorsal view. No. 16039, U. S, National Museum. Cape 
Cod, Mass. Collected by the U. 8. Fish Commission. 
PLATE 2. 
FiGureE 1. Cranium of the type of Sibbaldius tectirostris Cope. Ventral view. 
FIGURE 2. Cranium of Balenoptera physalus (L.). Ventral view. No. 16045, U. S. National Museum. Cape 
Cod, Mass. 
FIGURE 3. Cranium of Balenoptera physalus (L.). Ventral view. No. 16039, U.S. National Museum, Cape 
Cod, Mass. 
PLATE 3. 
FIGURE 1. Cranium of Balcenoptera physalus (L.). Dorsal view. Cape Cod, Mass. Ward’s Natural Science 
Establishment, Rochester, N. Y. 
FIGURE 2. The same. Ventral view. 
FIGURE 3. The same, Lateral view. 
PLATE 4. 
FiGurRE 1. Cranium of the type of Sibbaldius tectirostris Cope. Lateral view. 
FIGURE 2. Cranium of Balcenoptera physalus (L.). Lateral view. No. 16045, U.S. National Museum. Cape 
Cod, Mass. 
FIGURE 3. Cranium of Balcenoptera physalus (L.). Lateral view. No. 16039, U.S. National Museum. Cape 
Cod, Mass. 
FiGurE 4. Bones from the type-skeleton of Sibbaldius tectirostris Cope. Right first rib (double-headed), first 
lumbar, first dorsal, and axis. 
PLATE 5. 
Ficure 1. Cervical and dorsal vertebree of the type-skeleton of Sibbaldius tectirostris Cope. 
FIGURE 2. Lumbar vertebrz of the same. 
FIGURES 3 and 4. Caudal vertebrae of the same. 
PLATE 6. 
FIGURE 1. Ribs of the type-skeleton of Sibbaldius tectirostris Cope. 
FIGURE 2. Left scapula and humerus of the same. 
FIGURE 3. Right first rib of the same (double-headed). 
FicurE 4. Anterior portion of the skeleton of Balenoptera velifera (?), from behind, showing the ribs, 
sternum, etc., in position. Coast of California. Wistar Institute, University of Pennsylvania. 
311 
