E. LÖNNBERG, MAMMALOGY OF ECUADOR. 37 



evidently 30,6 % (not »about 20 %) of the first; and 87,3 % (not 

 »about 66 %») of the second. These percentages agree well 

 witli the corresponding ones före some merabers of Urosciurus, 

 and they cannot serve as distinguishing generic characters. 

 As I have not sufficient material for comparison, I cannot 

 judge, whether there are any other characters of importance 

 distinguishing »Hadrosciurus» from »Urosciurus» as two se\)R- 

 rate genera. The available descriptions do not convince me 

 about it. After the reduction in value of such an applica- 

 tion of the relative measurements of the nasals the main 

 difference between »Urosciurus>> and »Simosciuriis» appears 

 to b*e in the shape of the tail. It is rather a matter of taste, 

 if this should be recorded as sufficient. Until a renewed 

 investigation may settle the true relationship, I have provi- 

 sionally retained the name »Simosciurus». 



Rattus rattiis Lin. 

 1 (^ 7i 1913, Quevedo. A quite typical specimen. 



Ichthyomys södevströmii Thomas. 



Two male specimens both »taken alive at a spring» resp. 

 Ve 1913 and ^4 1914 at the same locality »Guapulo» below 

 Quito 8,800 feet altitude. 



Åiiotomys leaiider Thomas. 



5 »caught in a pool of fresh water, at La Carolina, north 

 of Quito, at an altitude of 9,400 feet, ^Vs 1918. It was very 

 valuable to obtain a specimen of this rare and very inter- 

 esting aquatic rat. It is, however, only little to add to Tho- 

 mas description (Ann. & Mag. N. H. (7) XVII, 1906 p. 86). 

 The white spöt sits behind and a little higher than the aural 

 slits, which appear to be closed by means of a fold or valve, 

 and there is no trace of an ear-conch. Thomas says: »Tail 

 well-haired» — , and this is certainly true, but it is especially 

 the case on the lower side, where the hairs are much longer 

 than on the upper. By this the tail evidently gains impor- 

 tance for the aquatic life as a rudder. 



