14 PROCEEDINGS OF THE ACADEMY OF [1889. 



OBSERVATIONS UPON THE DEVELOPMENT OF THE SKULL 



IN NEOTOMA FUSCIPES ; A CONTRIBUTION TO THE 



MORPHOLOGY OF THE RODENTIA 



BY R. W. SHUFELDT, C. M. Z. S. 



While collecting in the vicinity of San Bernardino, California, 

 daring the spring of 1887, Mr. F. Stephens secured a female speci- 

 men of Neotoma fuscipes which was far advanced in pregnancy at 

 the time of capture. 



From this source I obtained an embryo of this wood rat, and am 

 under great obligations to Mr. Stephens for the opportunity it has 

 given me to record something in reference to its developmental anat- 

 omy, and my observations upon it will form the subject of the pres- 

 ent paper. 



Neotoma fuscipes is by no means a common species, being restricted 

 in its geographical range to certain parts of the Pacific coast and 

 northern Mexico. I have never personally taken this represen- 

 tative of the genus, but I have on numerous occasions secured its 

 near relative, the form found throughout New Mexico, Neotoma 

 cinerea, of which I have a series of skeletons at my hand, of my own 

 preparing. 



Just prior to birth, the embryo of N fuscipes is quite hairless, and 

 measures in its total length about 4cms between vertex and tip of 

 tail, presenting all the general characteristics of the embryo of this 

 genus of the Murida?. For its total length, the head measures 1 

 centimetre and some few millimetres and in drawing my plates 

 which illustrate this account of its skull, I have enlarged these 

 parts six diameters. 



In working out the skull of this little rodent I have had to make 

 constant reference to the following works, which, though the only 

 ones available to me at the time, by no means pretend to be a com- 

 plete bibliography of the subject, while, on the other hand, they 

 constitute the best aids we possess to embryological research upon 

 the mammalia : 



Allen, Harrison, M. D. On a revision of the Ethmoid Bone 



in the Mammalia. Bull. Mus. Comp. Anat. Harvard 



College, Cambridge, Mass. Nov. 1882, pis. 1-7, pp. 135- 



164. 

 Balfour, F. M. A Treatise on Comparative Embryology. 



London, 1881. 



