ANATOMY OF MEGAPTERA LONGIMANA. 63 



been carefully dissected, but the circumstances attending the 

 dissection of large whales are generally not very favourable. 



Explanation of some of the Measurements in Tables II. and III. (pp. 64-67.) — 

 No. 1. Vertically from top of spinous process to back part of the bodj', or, when 

 spine very sloping, to level of under surface of body. In neck to level of lowest 

 part of body. 



No. 3. By callipers, from within spinal canal, along middle line of process. 

 From within canal is the only definite point below. In the cervical vertebrae 

 the thickness of the lamina is then deducted, as this had been done in the 

 measurements given in my table of the cervical vertebrai in this Journal in 1872, 

 pp. 20, 21. 



No. 9. When, as in B. musciilus, the measurement would differ according as 

 taken from where the process leaves the fore part or the back part of the body, it 

 is taken from a line drawn between these two points. 



No. 13. With callipers, towards the middle of the ends. At the margins it 

 might have been | to | inch less. 



No, 14. At anterior end, and on the edges of the epiphyses. At the middle 

 woulcl be less reliable, as some have a ridge, some a hollow there. At the 

 epiphysis keeps clear of the chevron tubercles. 



No. 15. At anterior end, and on the epiphyses. Just behind the epiphyses 

 might give \ to | inch more, but the epiphysis is the least variable part, and 

 will form the true end of the consolidated bone. 



No. 17. Taken, like No. 16, at the middle. Taken below or above the trans- 

 verse process according as it is before or behind the transition vertebra ; the 7th 

 of Megaptera, the 6th of B. musculus. 



No. 18. This measurement may be influenced to the extent of about I inch by 

 a superior median ridge, or by the top of the arch being a little more or less 

 pointed. 



No. 20. Between upper edges at fore part, being the most prominent part 

 anteriorly. In the neck, where the upper margin becomes the outer, the 

 measurement is between the outer margins of the anterior processes. 



No. 21. This measurement, taken with No. 1, shows the contribution made by 

 the chevron bones to the two-edged knife, or " razorback," form of the caudal 

 region in B. musculus, compared with Megaptera. 



Bodies of the Dorsal and Lumbar Vertebrae. 



4. Length, Breadth, and Height of the Bodies.^— On 

 referring to Table II. it will be seen that the largest bodies are 

 those of the first three or four caudal vertebrae. This part is 

 the foundation of the great propelling organ. It is at the 

 junction of about the posterior with the middle thirds of the 

 entire carcase in Megaptera. The greatest breadth (11 inches) 

 is attained by the 2nd and 3rd ; the 1st and 4th only | inch 



^ The epiphyses of the bodies are still ununited throughout the spine. The 

 ends of the spinous and transverse processes, and the upper margins of_ the 

 articular processes, all show evidence of unfinished ossification. 



