ART. 27 



ASYMMETRY IN SKULLS OF MAMMALS HOWELL 



11 



inward and upward growth of the roots of the tooth and the altera- 

 tion of its shape. 



Of significance is the practical nondevelopment of the outer ptery- 

 goid plate upon the left, following the destruction of function of the 

 muscles normally attached to it. A more detailed description of the 

 individual bones of the skull, although of interest, is hardly suffi- 

 ciently instructive for presentation here. 



ASYMMETRICAL SKULLS OF PINNIPEDS 



It is through the kindness of Dr. J. Grinnell that the writer has 

 been enabled to study the pathological skull of a sea lion from the 

 collection of the Museum of Vertebrate Zoology (pis. 5, 6, and 7). 

 This is a male specimen of Eumetopias juhata (Schreber), adult 

 but not aged, and evidently somewhat stunted by its condition. It 

 now bears the data "No. 4964, Museum of Vertebrate Zoology, 

 July 2, 1907, Ana Nueva Id., California, John Rowley, 257." In 

 asymmetry it is far more spectacular than the skull of the gorilla 

 already discussed, but its condition is considerably easier of inter- 

 pretation. 



The specimen was probably shot, as evidenced by a hole in the 

 right frontal and a larger one obliquely opposite within the orbit. 

 In addition it seems that the skull has since been dropped upon a 

 hard surface, for the cranium is badly fractured. John Rowley, the 

 collector of the specimen, writes (MS) that it "was apparently as 

 fat and husky as any of the others." The only evidence of old scars 

 upon the skull is to be found in the posterior half of the left zygo- 

 matic arch, and upon the medial portion of the left glenoid fossa. 

 It is possible that there was also partial fracture along the suture 

 formed by the left jugal with the maxilla, for this is now obliter- 

 ated, whereas it is strongly defined upon the opposite side. 



Although no full tables of measurements of the four skulls herein 

 discussed have been thought necessary, a number of the most signifi- 

 cant ones of the abnormal sea lion, compared with a normal one 

 which is somewhat larger, but probably of about the same age, are 

 found to be of interest. 



Total length 



Rostral width 



Exoccipital to anterior border of canine "{left ~ 



Length of jugal {Mt^^:: 



Total length mandibular ramus \\^t ~ ~ 



