No. I.] SKELETAL A lY ATOMY OF AMPHIUMA. 23 



endolymphaticus of considerable size ; but those of the opposite 

 sides do not come into contact. 



There are at this stage rudiments of two nasal glands. Each 

 consists of a single duct, which opens into the floor of the cor- 

 responding nasal-sac and passes directly inward so as to lie 

 finally upon the outer edge of the anterior end of the ethmoidal 

 plate. Here it divides into two tubes, which may be traced for 

 a short distance backward along the inner side of the nasal-sac. 



II. The Axial Skeleton. 



The vertebrae are undergoing ossification, and this is more 

 advanced in the anterior, than in those of the pelvic, region. 

 The bodies of the vertebrae are invested with a layer of bone 

 which closely surrounds the notochord. Toward the ends of 

 the vertebra the bony sheath expands a little, so that the verte- 

 bral body is somewhat hour-glass shaped. There is in the 

 centre of each vertebral body a portion of vertebral cartilage, as 

 represented by Dr. Wiedersheim in his Comparative Anatomy as 

 belonging to the vertebra of GyrinopJiiliis porphyriticiis. Out- 

 side the notochordal sheath, at the ends of each vertebra, is a 

 ring of much-modified intervertebral cartilage. The cartilagi- 

 nous arches of the vertebras come down upon the bony sheath 

 of the centra, and the bone rises up from the centra upon these 

 arches two-thirds the distance to their upper ends. 



There are no traces of ribs. Above the base of each lateral 

 half of some of the anterior vertebral arches there stands out a 

 process to which the future rib will possibly be attached. 



III. The Appendages. 



The shoulder girdle consists of two lateral masses of carti- 

 lage, in each of which may be distinguished a scapula, a cora- 

 coid, and a precoracoid. The scapula is slender, and is directed 

 downward and forward. The precoracoid is somewhat longer 

 than the coracoid. Both are considerably broader than the 

 scapula. They are widely removed from each other in the 

 middle line below. There is no suggestion of a sternum. 



The humerus has its shaft ensheathed in a thin layer of bone. 



