BAL.ENOPTERID.?!. 



Ill 



" As to the number of vertebra?, a small amount of latitude may 

 usually be allowed on account of the diiRculties connected with the 

 terminal bones of the tail. Very often in specimens in museums 

 several of these are wanting, owing to carelessness in preparing the 

 skeleton ; and, by a less excusable carelessness, the circumstance may 

 not be noted in published accounts of the number of vertebra pos- 

 sessed by the specimen. But even if all are present, slight discre- 

 pancies in enumeration readily occur. In early periods of life, the 

 last vertebra, although certainly formed in cartilage, is not ossified, 

 and the penultimate has so much the appearance afterwards assumed 

 by the last, as frequently to be taken for it ; or, again, later in Ufe 

 two or even three of the terminal vertebral elements grow together 

 so as to form a single osseous mass, which is counted as one or several 

 bones according to the discretion of the observer. Therefore, even 

 in well-described skeletons, a discrepancy of one or two in the given 

 number of caudal vertebrae is of no great consequence ; but there is 

 no evidence to prove the occurrence of any greater variation in any 

 given species,"— i^/ower, P. Z. S. 18G4, 388. 



I 



Upper surface of nasal bones of ^^^lales of different genera, ^^i\\ nat. size. 



a. Balmia 3Iysticetm. Mus. Roy. Coll. Surg. 



h. Huntirim. Mus. Leyden. 



c. Alet/fiptera loiit/imciiia. Mus. Brussels. 



(I. Fhj/sdiiis antiqiiontm. Mus. Roy. Coll. Surg. 



e. SibbukUiis SchlvyeUi. Mus. Leyden. 



/. BaUenoptera rostrata. Mus. Roy. CoU. Surg. 



Flower, P. Z. S. 18G4, 390. 



