7. SIBBALDIUS. 10!) 



with the additional two caudal vertebne, the wide maxillaries, the 

 more elongated metacarpals, and the slight dift'erences in the form 

 of the cervical vertebrae and the ribs, are sufficient to establish a 

 well-marked species ; and, unless it can be identified with any that 

 has been previouslj' described, I would suggest the name of latirosfris 

 as an appropriate designation." — Flower, P. Z. S. 1864, 411-414. 



B. Vertehrte 55. The first rib double-headed. 



7. SIBBALDIUS. 



The pectoral fins moderate. The second cervical vertebra with a 

 broad elongated lateral process, perforated at the base. The first 

 and second ribs double-headed. Lower jaw compressed, high, flat 

 on the sides, with a conical coronoid process. Vertebrae 55 or 56. 

 Ribs 13 . 13 or 14 . 14. 



Balsenoptera, sp., Gray. 



Pterobalfeua, sp., Eschricht, Van Bcneden. 



Sibbaldus, Gray, Proc. Zool. Soc. 1864, 223 ; Ann. 8f Maq. N. H. 



1864, xiv. 352. 

 Sibbaldius, Flower, Proc. Zool. Soc. 1864, 392. 



Pectoral fin one-eighth of the entire length; and the dorsal fin, 

 '' opposite the opening of the vent," nearly three-fourths of the entire 

 length from the nose. Skull very broad. Maxillary bones very 

 broad, gradually tapering, with nearly straight outer edges. The 

 intermaxillaries moderate, linear. The frontal bones broad, band- 

 like, with a wide sinuous edge over the orbits. Nasal bones small. 

 The lower jaw slightly arched, compressed, with a conical ramus 

 near the condyle. The lateral process of the second cervical vertebra 

 expanded, with a basal perforation (Rudolphi, Berl. Trans. 1822, 

 t. 1. f..2). Tympanic bone oblong, ventricose (see Dubar, t. 4. f, 1 ; 

 Rudolphi, t. 3. f. G). The lateral processes of the second to the sixth 

 cervical vertebrae separate, elongate. The arm-bones strong, the 

 forearm-bones nearly double the length of the humerus. The sca- 

 pula broad, with a large, well-developed coracoid process in front. 

 The hand with four rather short fingers ; the second and third equal 

 and longest ; the inner or fourth rather shorter than the first. 

 Phalanges 4.5.5.3. Vertebne 54. Ribs 13 or 14. The first rib 

 slender, with a process on the side near the condyle, as if the rib 

 was divided into two somewhat similar lobes above (Rudolphi, t. 5. 

 f. 6). According to Diibar, the first rib is articulated to the first 

 and second dorsal vertebrae. 



The under jaw less curved ; but the great character is that the 

 front rib is split into two separate parts near the condyle, or double- 

 headed as Dubar calls it. The tympanic bones are short, oblong, 

 swollen (figured in situ in the skull, Rudolphi, I. e. t. 3. f. 6). 



" Total number of vertebra? 56-58. Ribs 14 pairs. Orbital pro- 

 cess of frontal bone nearly as broad at outer end as at the base. 

 Nasal bones elongate, narrow, flat, or very slightly hollowed on the 

 sides of the upper surface, obliquely truncated at the anterior end 



