Mr W. S. iVJacLcay on Ceratitis Citriperda. 475 



slightly elevated tubercles, a row of which, of larger size, occupies the 

 middle line of the series, and is bordered on the outer and inner sides 

 by smaller ones. The crown of the first molar has three middle tuber- 

 cles; three external, the anterior and posterior of which are small; and 

 two internal : the second molar has two middle, three external, and two 

 internal tubercles : and the third molar exhibits one middle, two internal, 

 and one posterior, tubercles. 



A comparison of this description with the teeth of the Mus Musculus, 

 Linn., will suffice to show that no essential difference exists between 

 these organs in the two animals ; and they consequently both belong to 

 the same genus. The cranium of Mus Barharus, it may be added, 

 is comparatively more elongated than that of M^is Musculus : its length 

 is one inch and three Hues; its greatest breadth, six lines; its breadth 

 between the orbits, two lines and a half; and the width of the zygomatic 

 arches nearly eight lines. 



The accompanying figure, Tab. xvii, was taken from one of the spe- 

 cimens at present living in the collection of the Zoological Society. 



Arv. LX. Notice of Ceratitis Citriperda, an Insect very 

 destructive to Oranges. By W. S. MacLeav, Esq., 

 A.M., F.L.S., b^,c., in a Letter to the Editor. 



My dear Vigors, 

 It argues but little acquaintance with the gratification that may be 

 derived from the study of Natural History, to confine our researches 

 within what we may deem to be the sphere of its practical utility. The 

 Naturalist is the Historian of facts ; and to him it ought little to matter 

 whether these facts be of apparent utility or not. It is his duty to re- 

 cord them all, because he can never be sure that any are to remain abso- 

 lutely without importance, or that some one of his successors in the 

 science may not have occasion to make use of them. If even he should 

 be fortunate enough to make a new observation, having an immediate 

 bearing on the conmion purposes of life, he is not to suppose that he 



