1902.] OP THE SHORT-NOSED SPERM-WHALE. 57 



The two ends are rough and evidently had cartilaginous con- 

 tinuations. One end is broader than the other, and is apparently 

 the lower extremity : one surface is flat, and this I take to be 

 the external surface ; the other is very convex from side to side 

 (see PI. II. fig. 2, a), meeting the flat surface in a more or less 

 sharp edge ; one edge, the anterior, being much sharper than the 

 other. 



The general form of this little bone agrees very closely with 

 the shape of that region of the 12th rib just distal of the 

 curvature ; here the outer surface is flat and the inner surface 

 convex, the outline of a transverse section being (as shown in 

 PL II. fig. 2, a) similar to that of the above small bone. 



Further, I discovered a narrow, curved cartilage, four inches 

 (100 mm.) in length, pointed at one end, truncated and slightly 

 excavated at the broader end, which fitted on to the broad end of 

 the small bone. There is no doubt in my mind but that this 

 bone and cartilage constitute part, and the greater part, of the 

 13th rib of the left. side ; the upper end of which must have been 

 connected to the 1 3th thoracic vertebra : the connection was 

 probably by means of cartilage, for this narrower upper end of 

 the bone is rough and convex. 



On re-examining this vertebra, I noticed that the end of the 

 transverse process is similar to that of the 12th, and unlike that 

 of the succeeding vertebra, in that it has a small articular surface 

 on the left side, but none on the right side. 



We have here, I think, an explanation of the discrepancy as to 

 the number of thoracic vertebrse ; for, except in a very carefully 

 macerated skeleton, this little bone would undoubtedly be over- 

 looked ; and in skeletons lying on the shore there is little 

 likelihood of this last rib being found. Wall's figure, however, 

 is erroneous in that he places the last rib (the 14th according to 

 his enumeration) in line with the lower end of the preceding ; 

 but from the form of the bone and its resemblance to that part of 

 the preceding rib, I think that it lay higher up, in the position 

 indicated in PL II. fig. 2, with a long strip of cartilage below, 

 and a shorter cartilage (which I did not succeed in recovering) 

 above. 



In Wall's specimen this last small rib measured 1| inches, and 

 the preceding rib 11| inches. Krefft, too, notes that the last 

 rib, the 1 3th, is but 4 inches in length, whilst the preceding is 

 12 inches. It is not stated whether the measurement of the rib 

 was taken along the curve, or in a straight line from the capitulum 

 to the free end, but presumably it was in the former manner. 



In my specimen the 12th rib is 9 '6 inches (235 mm.) along 

 the outer curve, or in a straight line 8| inches (215 mm.), and 

 the bony part of the 13th rib is 1| inches (37 mm.). I estimate 

 that the total length of this rib, with both upper and lower 

 cartilages, was about 8 inches (200 mm.). 



We may then conclude that in Cogia there are 13 thoracic 

 vertebrse, with 12 pairs of complete ribs articulating with the 



