THE CETACEA. 335 



bone, on tlie other hand, which bounds the orbit below, is ex- 

 ceedingly slender. The very large maxilla extends backward 

 and outw^ard in contact with the frontal, or even overlapping 

 the greater part of its surface ; and it stretches forward to 

 very near the anterior end of the snout, so that almost the 

 whole of the gape is bounded by the maxilla. 



The premaxillge, on the other hand, though very long, inas- 

 much as they occupy the whole length of the jaw in the mid- 

 dle line, from the anterior nasal aperture to the end of the 

 snout, are almost entirely excluded from the gape. 



The nasal bones are always short; and, sometimes, are 

 mere bony tuberosities united with the frontal bones behind 

 the anterior nasal aperture. The turbinal bones are almost 

 always rudimentary, and the nasal passages are nearly verti- 

 cal, in consequence, for the most part, of the rudimentary con- 

 dition and shortness of the nasal bones. 



The periotic bones are loosely connected with the squa- 

 mosal and tympanic, and are usually united with the other 

 bones of the skull only hy cartilage, so that they fall out very 

 readily in the dry skull. The tympanic bones are commonly 

 of very considerable size, thick and scroll-shaped. 



The lower jaw has hardly any coronoid process, and its 

 ramus has no perpendicular portion, the condyle being situated 

 upon its posterior extremity. The body of the hj^oid is a very 

 broad plate of bone, and has tw^o j^air of stout, well-ossified 

 cornua. 



The Cetacea are devoid of clavicles. If the spine of the 

 scapula is present, it is a low ridge situated close to the ante- 

 rior edge of the bone ; but it commonly terminates in a long 

 acromion process, and, sometimes, there is a conspicuous, 

 straight, and flattened coracoid. The humerus is short, and 

 the articular surfaces at its distal end are, in all recent Cetacea, 

 flat facets inclined to one another at an angle. The ulna and 

 the radius are short, laterally-compressed bones, without any 

 movement upon one another ; and, in all recent Cetacea, they 

 are not freely movable upon the humerus. The carpus is often 

 imperfectly ossified. When the carpal bones are complete, 

 they are polygonal and imbedded in a fibrous tissue ; not 

 united b}^ articulations provided with synovial membranes. 

 The digits do not exceed five in number, but there are always 

 more than three phalanges in some of them. 



The pelvis is represented by two bones which lie parallel 

 with the axis of the vertebral column, give attachment to the 

 corpora cavernosa in the male, and, therefore, probably vepre- 



