170 



BALiENOPTERID.^. 



(fig. 13, «, p. 111). Lacrymal bones thickened and I'ounded at the 

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

 obtusely triangular coronoid process. Nem-al arches of the cervical 

 vertebrae 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 first dorsal vertebra} 

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

 cesses. Sternum verysmall, short,and broad, somewhat lozenge-shaped 

 (fig. 12, b, p. 110). Stylohyals very broad and flat (fig. 48, p.l84). 

 " Type species, aS^. laticeps, Graj':'—FJo2i'er, P.Z.S. 1864, 392, 393. 



J,/. ^././,,.M^ "-'*'• ^■""" 



SibbakJius laticeps (from Rudolphi) 



t. 26. f. (j. 



Professor Schlegel seems to think that the bifurcation of the fii'st 

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

 specimens of the BaJanoptefa PJu/sahis this bifurcation is grown to 



one solid mass This singular character has often induced me to 



beheve tliat the first rib, as it is called, is only the horns of the os 

 hyoides." — Letter, 24^/t A^gmt 1864. 



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

 as the " Ostend "VMiale" had the bifurcation Avell developed. 



* Dorsal Jin compressed, fulcate, two-thirds of the entire length from the nose. 

 Hibs 13 . 13. First rib short, dilated at the sternal end. Sternum with 

 an elongate, narrow posterior lobe. Rudolphius. 



1 . Sibbaldius laticeps. 



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

 as long as the ■^'idth of their base in front of the orbits ; the lower 



