126 IOWA ACADEMY OF SCIENCES. 



one not to be had in unlimited quantity. Also to secure careful dissecting 

 and not mere cutting and slashing. 



A "Study of the Brain of the Common Striped Squirrel," by Mr. T. J. 

 Kerr of the class of 1890, yielded the following results that may be worthy 

 of record, though it needs the drawings prepared in the study to fully exhibit 

 the results. 



The brain was studied especially in comparison with that of the rabbit as 

 described by Parker (Zootomy, pp. 365-379). 



The brain in general differs from that of L. cimiculus in being a little 

 broader in proportion to its length. The olfactory lobes are smaller, shorter 

 and more angular in outline. As the depressions on the ventral surface 

 between the lobes of the cerebral hemispheres and the white bauds connect- 

 ing the olfactory lobes with the temporal are very shallow, the surface is 

 smoother than that of L. cuniculus. The frontal and parietal lobes do not 

 show on the ventral surface as much as they do in the rabbit. 



The number of convolutions in each division of the cerebellum varies in 

 different bi-aius. The least number observed in the superior vermix was 

 six, the greatest eleven, the average being about eight. The least number 

 for each lateral lobe seven, the greatest fifteen, the average being about ten. 

 For each flocculus the least number was four, the greatest eight, the average 

 being about six. The vertical longitudinal sections present the usual tree- 

 like appearance or arbor vitre. The vertical transverse sections are less 

 tree-like in appearance. 



In L. cuniculus there is a slight elevation on which the pituitary body 



rests, but in S. iridecemlineatus there is a slight depression, a sort of nest. 



The corpus callosum is a strong white transverse baud connecting the 



cerebral hemispheres. It is about half as long as the cerebrum, instead of 



one-third as long, as in L. cuidc7ihis. 



The peduncles of the pineal body are thin white bands on the posterior 

 two-thirds of the upper surface of the optic thalami, instead of one-half as 

 in L. ctmiculus. The two peduncles unite at the posterior boundary of the 

 thalami and then pass backward and upward to the pineal body. 



The optic lobes or corpora quadrigemina are two pair of rounded lobes 

 lying just above the crura cerebri, just posterior to the optic thalami and 

 third ventricle, just below the hippocampi majores and dorso-posterior part 

 of the parietal lobes and just anterior to the cerebellum. The nates, the 

 larger pair, lie almost entirely above the testes, instead of anterior to, as in 

 L. cuniculus. As seen from behind after removing the cerebellum the testes 

 are transversely elongated as in the rabbit. 



The brain of the pocket gopher, studied by Mr. W. E. Harrimau of the 

 class of 1893, was compared particularly with that of the rabbit, as detailed 

 by Parker (Zootomy, pp. 376-397), and with that of the striped gopher as 

 given by Mr. Kerr in the paper previously quoted. 



The brain of the pocket gopher (Oeomys bursarius) is moi'e nearly the 

 shape of the brain of L. cuniculus than of SpermopJiilus tridecemlmeatus, its 

 width being less than is the same dimension in S. tridecemlineatus. How- 

 ever, it resembles the latter in point of there being comparatively smaller 

 parietal lobes than in L. cuniculus. The dimensions, as averaged from 

 measurements of thirteen brains, are as follows: Antero-po^terior (from 

 anterior end of olfactory lobe to posterior end of medulla) twenty-six milli- 



