181 



ramus which exists also, but in a more moderate degree, in Ca- 

 promys ; in the Capybara we see indications of a similar structure. 

 An immense space is here aiForded for the insertion of the temporal 

 and masseter muscles : these muscles may be short, but their strength 

 will be prodigious. In the Beaver the coronoid processes are long 

 and rise above the condyles : in the Capyhara they are short and on 

 a level with the condyloid processes, which are themselves very con- 

 tracted : in Capromys they are very small : but in the Coypus the 

 coronoid processes are reduced to a mere rudiment, elevated by the 

 side of the last molar tooth. On the contrary the posterior angle 

 here stretches back in a flat narrow process continued from the la- 

 teral shelf, or, as we may term it, horizontal reflexion of the lower 

 margin of the ramus. 



" The dentition of the Coypus is figured by M. F. Cuvier in his 

 work ' Sur les Dents des Mammif^res.' It difi^ers widely from that 

 of Hydromys, with which the animal was associated generically by 

 M. Geoffroy St. Hilaire. Cuvier observes, that the skull of the Coy- 

 pus has a resemblance to that of Hystrix dorsata : I have not seen 

 a skull of this animal and therefore cannot judge, but certainly the 

 teeth as given by M. F. Cuvier and those of the Coypus materially 

 diff^er. The molars in the Coypus are four on each side above and 

 below. In the upper jaw they have an outward inclination ; the 

 last is the largest, and they decrease in size slightly but regularly 

 from the last to the first : each is a copy of the other; and the rib- 

 bands of enamel are oblique. The molars of the lower jaw incline 

 obliquely inwards, and decrease in size from the last to the anterior. 

 The incisores are large and strong and of a deep orange yellow on 

 their outer surface ; the alveoli of those of the upper jaw pass through 

 the intermaxillary into the true maxillary bones. In the lower jaw 

 they extend beneath the whole row of the molares. 



" Of the rest of the skeleton, the trunk, clavicles, scapula, humeri, 

 and femoral bones are all that I have been able to examine, the rest 

 being contained within the mounted specimen. 



" The scapula agrees closely with that of Capromys, but diff'ers 

 considerably in shape from that of the Beaver. Its anterior edge 

 runs out into an angle, at a greater comparative distance from 

 the spinous ridge than either in the Beaver or the Porcupine; 

 and the same may be said of the posterior angle : so that the 

 total breadth of this bone is comparatively greater than it is in 

 those two animals. Its length from the glenoid cavity to the pos- 

 terior angle is 2^- inches. Its breadth from this angle to the oppo- 

 site 2. The spinous ridge is thin and but little elevated; about the 

 middle it is slightly dilated. Three quarters of an inch before it 

 reaches the level of the glenoid cavity it ceases ; the acromion 

 process being here united to it by cartilage in the specimen be- 

 longing to the Society. I find, however, that this cartilaginous 

 union at some period of the animal's existence becomes ossified ; for 

 in a clavicle belonging to Mr. Blackett the acromion is completely 

 anchylosed to the extremity of the spine. This process is at first 

 slender, but it spreads at its termination into a broad triangular base, 

 to the anterior apex of which is attached the clavicle. The length 



