EXPLANATION OF PLATES. 



PLATE 1. 



Figure 1. Cranium of the type of Sibbaldius teetirostris Cope. Dorsal view. Philadelphia Academy of 



Natural Sciences. 

 Figure 2. Cranium of Balnenoptera physahis (L.). Dorsal view. No. 16045, U. S. National Museum. Cape 



Cod, Mass. Collected by the U. S. Fish Commission. 

 Figures. Cramum of BalceiiojAem physaliis (L,.). Dorsal view. No. 16039, U. S. National Museum. Cape 



Cod, Mass. Collected by tlie U. S. Fish Commission. 



PLATE 3. 



Figure 1. Cranium of the type of Sibbaldius teetirostris Cope. Ventral view. 



Figure 2. Cranium of Balcenoptera jjhysalns (L.). Ventral view. No. 16045, U. S. National Museum. Cape 



Cod, Mass. 

 Figure 3. Cranium of Balcenoptera physahis (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. 



Figure 1. Cranium of the type of Sibbaldius teetirostris Cope. Lateral view. 



Figure 2. Cinnhim oi Balcenoptera physalus (L.). Lateral view. No. 1604,'), U. S. National Museum. Cape 



Cod, Mass. 

 Figure 3. Cranium of Balcenoptera physahis (L.). Lateral view. No. 16039, U. S. National Museum. Cape 



Cod, Ma.ss. 

 Figure 4. Bones from the type-skeleton of Sibbaldius teetirostris Cope. Right first rib (double-headed), first 



lumbar, first dorsal, and axis. 



PLATE 5. 



Figure 1. Cervical and dorsal vertebrse of the type-skeleton of Sibbaldius teetirostris Cope. 

 Figure 2. Lumbar vertebrje of the same. 

 Figures 3 and 4. Caudal vertebrae of the same. 



PLATE 6. 



Figure 1. Ribs of the type-skeleton of Sibbaldius teetirostris Cope. 

 FIGURE 2. Left scapula and humerus of the same. 

 Figure 3. Right first rib of the .same (double-headed). 



Figure 4. Anterior portion of tlie skeleton of Balcenoptera vclifera (?), from beliind, showing tlie ribs, 

 sternum, etc., in position. Coast of California. Wistar Institute, University of Pennsylvania. 



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