44 ARKIV FÖR ZOOLOGI. BAND 14. N:0 4. 



as being narrower than that of the common Paca with the 

 osseous cheek pouches less broadly developed and much less 

 rugged on the surface. As no measurements are publisbed, 

 and the exteriör appearance of the animal as well as its 

 habitat and origin are unknown, it is quite uncertain whether 

 this suhlaevis represents an individual variety (perhaps from 

 captivity) of the common Paca or something else. 



On the other hand this museum possesses a Paca from 

 Ararangua, S:a Catharina, Brazil, the skull of which com- 

 pletely agrees with Gervais' description of suhlaevis as far 

 as it goes. It is a rather old specimen with basal sutures 

 closed and molars well worn. In spite of its age the greatest 

 breadth of the jugale does not amount to more than 34,5 

 mm, while the corresponding measurement of another Paca 

 from the interiör of southern Brazil is 50,5 mm. The former 

 skull is also narrower so that the greatest breadth below the 

 orbits is 78, and at the posterior end of the expanded jugalia 

 81 mm, but in the latter resp. 95 and 96,5 mm. If to this 

 is added, that the skull from S:a Catharina is much smoother 

 as well on the zygomatic arches as on the frontals, which 

 both are very rugose in the other skull, it is apparent that 

 the former skull in comparison with the latter quite well 

 agrees with the short description which Gervais has given 

 of his suhlaevis. Now it is of importance to observe that 

 this specimen with the smooth skull is a female, as can be 

 stated from the nipples on the skin. It is thus very near 

 at hand to draw the conclusion that the smoothness of this 

 Paca skull as well as its more slender dimensions are due 

 to its female sexe. This is also confirmed by the fact, that 

 a female skull of Goelogenys sierrae Thomas in this museum 

 exhibits a similar condition with regard to smoothness and 

 slenderness, while a male skull of the same age and from the 

 same locality is much more robust and has very rugose sur- 

 faces to the zygomatic arches and the upper parts of the 

 skull. Furthermore two female Paca skulls in the present 

 collection from Consul Söderström are smooth and compa- 

 ratively slender, while the male skulls from the same region 

 are very rough and much larger. Considering these analogous 

 conditions observed on skulls from three different countries 

 in South America I do not think it too audacious to assume 

 that Gervais' name suhlaevis, meant to be specific, must be 



