OF BALiENOPTERA MUSCULUS. 



211 



upper and lower borders converge. It ends in two prolongations, of which the superior 

 rests on the intermaxillary hone, and the inferior, which is longer, reaches almost to the 

 maxillary — very possibly quite to it in the fresh state. The anterior surface is concave 

 from side to side, being inclosed by the median and lateral prominences. It becomes 

 narrow as it turns on to the upper surflice, and passes to the outside of a median triangular 

 elevation. The under surface is smooth and bounded anteriorly by an oblique line run- 

 ning forward and inward. When the two nasals are in position they form a prominent 

 spine in the median line. 



The greatest height (i. e., vertical length) taken near the posterior end is 10 1-2 inches. 

 The other dimensions can be found in the table of measurements. 



The Malar (PL vi, fig. 2 h). — This is a thin bone; broad in front, narrow behind ; 

 concave above, convex below. The lower surflxce is marked near its anterior end by a wavy 

 ridge which articulates with the posterior border of the superior maxillary. On front of 

 this ridge the malar is thinner and overlaps the adjoining bone. The upper surface bears 

 at its anterior extremity a depression for union with the lachrymal. The outer edge is thick ; 

 the inner thin. Towards the front of the outer border there is a deep notch, the con- 

 tinuation of a gi'oove on the upper surface. The greatest length of the bone is 9 3-4 inches; 

 It ends behind in a spine 3-4 inch long, pointing directly inward. 



The Lachrymal (PI. vi, fig. 2 I) is in shape an oblique parallelogram with rounded angles, 

 placed transversely between the frontal and the outer angle of the superior maxUla. It 

 helps to form the orbit anteriorly. Only a very small portion projects outwards. The 

 inferior surface presents a depression for articulation with the malar. 



Hie Mandible. — The lower jaw is very solid and heavy. It is strongly curved, the 

 greatest convexity being rather behind the middle. The head, which forms the posterior 

 end of the bone, is of ovoid shape, with the long diameter running downward and outward. 

 It is separated from the body by a groove running outward and a little downward on the 

 hinder aspect. The neck is constricted laterally, but the sides retain their convex form. 

 It is marked below by a rough line, above by a sharp ridge which runs forward and turn- 

 ing downward forms the edge of the roof of the dental canal, overhanging the entrance. 

 The coronoid process extends upward and outward and ends in a blunt knob. Its posterior 

 border is nearly vertical, its anterior is very oblique, and gradually subsiding forms the 

 superior division between the outer and inner surfaces. The body decreases in size very 

 gradually ; the outer surface is convex, the inner nearly plane, except near the anterior end 

 where its upper portion overhangs the inferior, forming a groove. The opening of the den- 

 tal canal is situated a little behind a line dropped from the posterior border of the coronoid. 

 A groove containing many small foramina runs along the upper part of the internal surface, 

 just inside of the bounding line. Several larger foramina are placed in a row on the upper 

 part of the convex outer surface. These latter are eight in number on the left side, and 

 eleven on the right. 



Hyoid. — The basihyal with the coossified tliyro-hyals presents the appearance character- 

 istic of the species. The body is nearly flat, and the thyro-hyals, at first very solid, taper 

 towards the end and are bent strongly upward. The anterior cornua which surmount the 

 body are nearly two inches long, and but about half an inch apart. There is a median 

 notch on the posterior border of the body with a slight tuberosity on either side. Its supe- 

 rior surface is deeply grooved in the middle. The antero-posterior diameter of the body in 



