1926] Hall: Skull of the Eodent Otospermophilus grammurus lecche>,i 361 



mere edge of the lacrymal extends up between the jngal and frontal 

 on the rim of the orbit, and gradually develops into the tuberele-like 

 pars facialis of adults. It measures 2 to 3 mm. anteroposteriorly in Q. 

 Within the orbit and immediately below the rim is the opening of the 

 lacrymal canal. The opening of this canal does not change its position 

 but the orbital ridge of the lacrymal overhangs it somewhat in old 

 specimens; thus in Q only a small part of the opening is visible when 

 the skull is viewed laterally. On the turbinal surface of this bone a 

 wing is sent out which finally encloses the lacrymal duct. The lacrymal 

 duct, then, runs not between the lacrymal and turbinal bones but 

 through the lacrymal bone, at least in specimens older than J. The 

 lacrymal lies on the surface of and overlaps the jugal, maxilla, frontal, 

 and turbinals. This superficial position together wdth the small size 

 of the lacrymals and the fact that strong contacts are formed between 

 the jugals and maxillae, and between the maxillae, premaxillae, and 

 frontals, indicate that the lacrymals do not play an important part 

 in transmitting the strains of the zygomatic arches to the other bones 

 of the skull. 



Frontals. — In A the anterior regions of the frontals, both dorsally 

 and on the lateral wings that lie within the orbits, are the only portions 

 ossified. In B the two frontals are largely ossified, but a large fon- 

 tanelle exists between them and the two parietals, and there is some 

 unossified tissue along the entire fronto-parietal suture. A supra- 

 orbital ridge and slight notch are present in B, but not until C ate 

 there slight indications of postorbital processes. In D these processes 

 are sharp and distinct. They are located about one-fourth of the 

 total length of the frontal anterior to the frontal border of the parietal. 

 From D to Q several changes gradually take place. These are : an 

 elongation that results in the processes becoming more slender in pro- 

 portion to their thickness, a movement that causes them to be inclined 

 forward and downward, and an incorporation of a part of a parietal 

 bone in the posterior border of each process. It is evident from its 

 situation in D (noted above), that some change has taken place in 

 the position of the postorbital process, relative to the position of the 

 parietal. This change is accomplished by each parietal overlapping 

 the frontal at the dorsolateral angle of the skull. When the parietal 

 reaches the postorbital process, a portion of the parietal is carried out 

 with the postorbital process to form a part of its posterior border. On 

 the dorsolateral face of skull no. 29640, which represents the L stage of 

 development, the parietal has overlapped the frontal for a distance of 

 5.7 mm., which is more than one-fourth of 22.1 mm., the total length of 



