170 



BAL^NOPTERID^. 



(fig. 13, e, p. 111). Lacrymal bones thickened and rounded at the 

 outer end. Lower jaw with a comparatively slight curve, and a low, 

 obtusely triangular coronoid process. Neural arches of the cer'vdcal 

 vertebi'ae high, and their spines well developed. Transverse process 

 of atlas arising from upper two-thirds of side of the body, short, and 

 deep from above downwards (fig. 41, p. 181 ; fig. 42, p. 182). On 

 the hinder border of the under surface a median pointed triangular 

 process, directed backwards and articulating with the axis. Upper 

 and lower transverse processes of the second to the sixth vertebrae 

 inclusive well developed, broad, and flat (united at their ends in the 

 adult, except the sixth ?). Lower process of the sixth short, broad, 

 and much twisted on itself. Head of the first rib bifurcated into an 

 anterior and posterior division, articulating with the extremities of the 

 transverse processes of the seventh cervical and fii-st dorsal vertebrae 

 respectively. Second, third, and fourth ribs with short capitular pro- 

 cesses. Sternum very small, short,and broad, somewhat lozenge-shaped 

 (fig. 12, 6, p. 110). Stylohyals very broad and flat (fig. 48, p. 184). 

 " Type species, S. latkeps, Gray r— Flower, P.Z.S. 1864, 392, 393. 



Flo-. 37 



Sibbaldius laticops (from Rudolphi). Cuv. t. 26. f. 6. 



Professor Schlegel seems to think that the bifurcation of the first 

 rib is a mark of youth, for he observes, " It appears that in old 

 specimens of the Bahmoptera Physalns this bifurcation is grown to 



one solid mass This singular character has often induced me to 



believe that the first rib, as it is called, is only the horns of the os 

 hyoides." — Letter, 24th Auguf^t 1864. 



I may observe, in reply, that the full-grown specimen described 

 as the " Ostend Whale " had the bifurcation well developed. 



* Dorsal jftn compressed, falcate, two-thirds of the entire length from the nose, 

 liibs 13 . 13. First rib shm-t, dilated at the sternal end. Sternum with 

 an elongate, narrow posterior lobe. Rudolphius. 



1. Sibbaldius laticeps. 

 Black, beneath white. Upper jaws wide, in the skuU only twice 

 as long as the width of their base in front of the orbits ; the lower 



