190 



consists of two cylinders, not disjoined in the middle where the bony 

 portion of the crown is continuous, but partially separated by a fold 

 of enamel on either side producing a corresponding notch ; placed 

 obliquely with respect to the jaw they resemble, in some measure, a 

 figure of 8 with its elements flattened obliquely, pressed towards 

 each other, and not connected by the transverse middle bars. With 

 the lower molars of Octodon those oiPoephagomys, as figured by M. F. 

 Cuvier, correspond in structure in both jaws. Octodon thus exhibits, 

 in its dissimilar molars, the types of two genera : the molars of its 

 upper jaw represent those of both jaws of Ctenomys ; those of its 

 lower jaw correspond with the molars of both jaws of Poephagomys. 

 The characters distinguishing the new species of Ctenomys are 

 chiefly those of colour. The Cten. Brasiliensis is described by M. de 

 Blainville as being shining rufous above, and reddish white below. 

 The new species may be characterized as the 



Ctenomys Magellanicus. Cten. flavescenti-fusco-griseus, subtits 



pallidior ; pedibus cauddque albescent ibus. 

 Long, corporis cum capite "7-1: unc. ; caudte, 2-I- ; capitis, 2. 

 ' ' Hub. apud Portum Gregory dictum, ad Fretus Magellanici ostium 

 orientale. 



Captain King states that this " little animal is very timid ; feeds 

 upon grass ; and is eaten by the Patagonian Indians. It inhabits 

 holes, which it burrows, in the ground : and, from the number of the 

 holes, it would appear to be very abundant." 



A second animal exhibited appears, like the preceding, to represent 

 in the more southern latitudes of South America a genus whose type 

 was originally observed in Brasil. Mr. Bennett regarded it as a 

 second species oi Kerodon, F. Cuv., chiefly distinguishable from the 

 one discovered by Prince Maximilian of Wied by its more uniform 

 colour. Excepting a slight dash of white behind the ear, and a 

 longer line of the same colour marking the edge of each branch of 

 the lower jaw, the animal is entirely grey ; the upper surface being 

 distinguished from the under by a greater depth of tint, and by the in- 

 termixture of a free grizzling of yeUow and black. The crowns of 

 the molar teeth, as in the typical species, consist of bone surrounded 

 by two triangles of enamel, the bases of which are connected together 

 by a short line of enamel passing from the one to the other : all the 

 lines being slender and sharply defined. 



For this species Mr. Bennett proposed the name of 



Kerodon Kingii. Ker. griseus, suprclflavo nigroque punctulatim 

 interstictus ; macula pone aures linedque ad maxillce inferioris 

 marginem albis. 



Long, corporis cum capite 9^ unc. ; capitis, 2'f ; auricula sub- 

 nulla. 



Hab. apud Portum Desire dictum, ad Patagonise littus orientale. 



The third animal exhibited was remarked on as constituting a new 

 species of Cavy, distinct from all those that were previously known, 



