ISO ESCHRICHT ON THE 



skeletons they cannot be distinguished, unless their ossification has reached the surface, and as 

 yet this was only the case with one of the bones of the very young specimen depicted. 



It has also been already indicated, that the ankylosis of the cervical vertebrae may appear 

 more or less extensive according to the animal's age, at least, after the cartilaginous portions have 

 been removed from theii* places, and I do not hesitate to express a similar opinion about the height 

 of the protuberance formed by the frontal and the nasal bones, as well as about the proportion 

 between the length and the breadth of the head ; for the greatest breadth of the head, namely, 

 between the temporal arches, is always inferior in less muscular individuals, whether this infe- 

 riority must be ascribed to age or sex. The number of the phalanges is, indeed, independent of 

 age, but not quite constant ; not unfrequently it is not even quite the same in the two pectoral fins of 

 the same individual. The same remark may also be applied to the number of the ribs, for 

 Mr. Thomsen's specimen has twelve ribs on the left, eleven on the right side. But yet it 

 cannot be denied that in addition to other and more certain characters, such uncertain or 

 inconstant ones as the number of the ribs and the phalanges may also deserve to be 

 considered. 



Thus, of the author's eight osteological characters, there is only one left to be considered, 

 we mean the one placed at the top of the list : the size of the individuals. It is true, that the 

 remark made by the author himself, that many of his characters may be explained as diiFerences 

 of age or sex, may be fully as well applied to this character, as to any of the others ; and the 

 author has, undoubtedly, as I shall have occasion to show immediately, been very unsuccessful 

 in bestowing this character on the skeletons in the museum under my care, but he was perfectly 

 right in using it in the comparison of Professor Nilsson's specimen with the two from Bergen ; 

 for here it is expressly stated, that the skeletons compared both belonged to full-grown males. 

 It is true, that a full-grown animal's teeth are continually wearing off to a considerable degree, 

 and that the animal itself may become far more muscular after having attained its full length, by 

 which means the different protuberances in the cranium may also increase in circumference, and 

 the head itself become broader ; but when the animal is really full-grown, that is to say, when 

 the epiphyses are ankylosed to their respective vertebral bodies, then it cannot increase in length. 

 And though we may find full-grown individuals of rather different sizes within the same species, 

 yet in individuals of the same sex, especially among the Cetaceans, we find these differences con- 

 fined within so narrow limits, that we may suppose, with considerable certainty, that two full- 

 grown males, the skeleton of one of which is 20' 4^" (2 1 J Swedish feet) long, and that of the 

 other only 14' 10" (15' 8 J" Swedish measure), can scarcely belong to the same species. When 

 this point has been settled, then, as has already been granted, we may also pay some regard 

 to the less constant characters, as the number of the ribs and phalanges. 



But before we enter on all the inferences implied by such a supposition, we ought 

 first to procure all the information that can possibly be obtained, in order to ascertain its 

 correctness. One of the most certain signs that a toothed-whale has attained its full 

 growth, is, in my opinion, its having its teeth closed at the roots, and the only part of 

 the skeleton, by which the sex of the individual may with any certainty be ascertained is, accord- 

 ing to what we have just stated, the pelvic bones. I have, therefore, applied to the excellent 

 director of the Bergen Museum, Dr. Koren, by whom these two skeletons were put up, and by 

 whom Professor Lilljeborg's attention, was in the first instance directed to the probability of the 

 Stourliynning being a different species from the Delphinus orca described by Schlegel. Dr. 



