363 



2003. The skeleton of the Guinea Pig (Cavia aperea). 



In this skeleton the vertebral formula is : 7 cervical, 13 dorsal, 6 lumbar, 3 sacral, and 

 6 caudal. The intercondyloid space of the humerus is perforated, but not the inner condyle. 



Purchased. 



2004. The skull of the Guinea Pig. 



The occipital foramen is relatively larger than in the Capybara, and of a subquadrate form : 

 two small notches at its upper part indicate the superoccipital to form a larger portion of its 

 circumference. The paroccipitals are well developed, but relatively shorter than in the Capy- 

 bara. The acoustic bullse are much more expanded. The squamosal presents a similar form, 

 and is equally distinct from the petrotympanic. The sagittal suture is obliterated : the frontal 

 one is retained. The nasal processes of the premaxillaries slightly expand at their posterior 

 extremities, which reach as far back as the nasals themselves. The antorbital vacuity is con- 

 siderable, and a depression above the anterior molar prominence conducts to the nasal cavity. 

 The lacrymal expands posteriorly into a partial capsule of the sac, and extends anteriorly 

 nearly across the bar, overarching the antorbital vacuity. The lower jaw, in its external ridge 

 and long posteriorly produced angle, repeats the characters of that of the Capybara, but the 

 coronoid and condyloid rise somewhat higher. 



Hunter ia a. 



2005. The skull of a Guinea Pig (Cavia aperea}. 



The auditory bullae are perforated externally beneath the meatus, this perforation answer- 

 ing to the lower division of the hourglass-shaped auditory aperture in the Capybara. 



Presented by Henry Cline, Esq. 



2006. The skull of a Guinea Pig (Cavia aperea). 



The molar teeth are removed from the left side of the upper, and from the right side of 

 the lower jaw, and separately displayed. The bony palate is more deeply excavated behind 

 than in the Capybara, and by a curved instead of an angular emargination. The ectoptery- 

 goids are more developed. The true molar series of the upper jaw meet anteriorly at an acute 

 angle. The four teeth are similar in size and structure ; each is divided into two lobes by a 

 fold of enamel, extending from the inner side almost across the tooth ; the outer coat of 

 enamel bends round the end of this fold, and slightly indents the outer side of the hinder 

 lobe or division of the tooth. The last molar is characterized by a slight production back- 

 wards of the outer angle of this lobe. The lower molar teeth resemble the upper ones 

 reversed ; that is, with the inner side turned outwards : both are curved and rootless, or with 

 persistent matrices ; the convexity of the upper teeth being turned inwards, those of the lower 

 teeth outwards, and the alveolar ridges corresponding in their relative breadth with the depth 

 of the folds which they penetrate. The incisors are not grooved along their enameled sur- 

 faces. 



Hunterian. 

 3x2 



