176 BAL^NOPTEBIDiE. 



This specimen was 102 feet long, the lower jaw 2H feet long, 

 and the fins 13|^ feet long. Vertebra 54. Ribs 14 . 14. The atlas 

 {Dubar, t. 6. f. 1) : the second cervical vertebra with large lateral 

 processes, pierced with a large hole ; the third, fourth, and fifth 

 with two lateral processes on each side, which are not formed into 

 a complete ring as in the second ; the fifth offers a rudiment of a 

 spinal apophysis. The first rib double-headed, articulated to the 

 first and second dorsal vertebrse. Bones of the ears (Dubar, t. 5. f. 1 ) ; 

 OS hyoides (t. 5. f. 2) ; breast-bone" (t. 6. f. 4) not pierced, short 

 and broad, with a broad hinder portion. The vertebral column 37. 

 Dubar's figures represent the second, third, and fourth cervical ver- 

 tebrse as with a ring, and the fifth, sixth, and seventh with deflexed 

 upper and straight lower separate lateral processes. Eibs, first (t. 8. 

 f. 1) with two heads, vei-y broad at lower end; second (f. 2) with 

 rather elongate internal process ; fourteenth (f. 3) quite simple. 

 Pelvic bones (t. 9. f. 1, 2). Shoulder-blade short and very broad 

 on the external edge, with a large lobe for the ridge (t. 10). Pectoral 

 fin and bones (t. 11). Fingers four ; the second and third nearly of 

 equal length, and longest ; the fourth or outer shorter, longer than 

 the first or inner. 



Fig. 39. 



First rib of Sibbaldim borealis. (From Dubai.) 



The upper jaw narrower and shorter than the lower, so as to be 

 embraced by the lower ; a tuft of homy round filaments or long hairs, 

 united at their roots by a common membrane and divided at the end 

 into small points, at the tip of the snout. Eyes rather high and 

 very near the angle of the mouth. Ear-hole near the eye, but a little 

 further back. Hinder part of the back keeled. Dorsal fin rather 

 less than three-fourths of the entire length from the end of the nose, 

 exactly opposite the vent. Skin polished, black above, white beneath. 

 Length (entire) 25 metres, of mouth 4-8, to pectoral 6-9, to navel 

 13-7, to front of vagina 18-1, to front of vent 18-1. Length of pec- 

 toral fin 3-1, width of pectoral 0'65. The atlas transverse. The 

 lateral processes thick, elongated, rather above the middle of the 

 side (Dubar, t. 6. f. 1). The os hyoides broad in the middle and 

 gradually tapering at each end, and with a deep notch in the middle 

 of the hinder edge (Duhar) {ScUarff's figure). Tympanic bone ob- 

 long, very imperfectly figured as the os clu rocher (t. 5. f. 1). The 



