OCR Text |
Show 1902.] OF THE SHORT-NOSED SPERM-WHALE. 59 In the present specimen (see PI. III. fig. 5) the bones and cartilage were uninjured. The basihyal is a flat, irregularly circular bone, notched in the middle line posteriorly, and with a pair of slight prominences at the anterior end, separated only by a shallow furrow ; each of these prominences bears a small tetrahedral cartilage, which evidently correspond to the bony projections seen in Physeter, but which in Cogia do not appear to ossify, for they are unrepresented in Y. Beneden's figure. The anterior cornu consists of two segments, viz.: a short proximal, curved cartilage, circular in section, representing the ceratohyal; and a much longer distal region, the middle of which ossifies to form the cylindrical stylohyal bone. The posterior cornu, as in Physeter, is a broad plate of cartilage, in the midst of which is a more or less circular flat bone-the thyrohyal bone. This posterior cornu is not segmented from the basihyal, the cartilage being perfectly continuous. Measurements. Basihyal bone: rnillim. Greatest breadth 84 „ length 66 Thickness 5 Length of cartilaginous process 18 Total length of each half of the basihyal + thyrohyal, from the anterior end of the cartilaginous process to tip of cornu 156 Greatest breadth, across the two posterior cornua, measured from the outer margins 188 Length of thyrohyal bone 55 Breadth of „ „ 46 Anterior cornu : total length 220 Length of ceratohyal cartilage (in middle line) 37 „ stylohyal segment 175 J} „ bone (along its middle) 65 „ „ hinder margin 75 Thickness 15 The Scapula. This bone has been figured more or less accurately by all the authors who have dealt with this whale, but without the cartilages. The scapula has the usual cetacean form (see PI. 1Y. fig. 6); its external surface is feebly concave, owing to the reversion of the anterior margin and of the superior border. The spine is but feebly developed, but the acromion is a large subquadrangular process. The coracoid process is large and well marked, not quite so long as the acromion. The glenoid cup is oval. The following measurements of the bone, without its cartilage, were made :- |