18/3.] ANATOMY OF AULACODUS. 7^0 



The specimen being a male, those generative organs only can be 

 described. The ureters enter the bladder at about one third its length 

 from the neck. The vesiculse seminales are two inches long, being 

 composed of tubes with irregularly situated lateral diverticula of small 

 size ; they enter the urethra separate from the vasa deferentia, which 

 are not swollen at their urethral ends. The testes are abdominal, 

 being situated at the entrances of the capacious abdominal rings, with 

 strong muscular gubernacula attached to the bottom of the would-be 

 scrotum. The epididymis of each testis is of about one fourth its size. 

 The prostate is, like that in most Rodents, composed of closely related 

 but not intercommunicating bundles of glandular substance, arranged 

 in elongated conical bundles, which can be easily separated from each 

 other, each being about two thirds of an inch long. The membra- 

 nous urethra is 3 inches long ; Cowper's glands are about the size of 

 peas, dark red aud subspherical. The os penis is half an inch long ; 

 and its free end forms part of a lip-like projection over the top of the 

 orifice of the urethra. 



There is a gland, the shape of the hearts on playing-cards, fixed at 

 its apex, which opens into the anterior wall of the termination of the 

 rectum, just within the sphincter ani; it is white in colour, and the 

 size of a haricot bean. 



The most striking peculiarity in the above described anatomy of 

 this animal is in the arrangement of the caecum, which differs from 

 that of most of the Cavies I have had the opportunity of examining in 

 not presenting an abrupt change in the character and direction of the 

 gut at the point of junction of the caecum and colon. Respecting its 

 osteology it may be mentioned that there are thirteen ribs, and that 

 the clavicle was not developed from end to end in this not fully adult 

 specimen, the sternal extremities being cartilaginous and joined to the 

 free termination of a broad cartilaginous spatulate manubrium sterni. 

 In a skeleton in the British Museum the broad bifurcate acromion is 

 not preserved on either scapula ; and they do not seem to have been 

 broken off. In the specimen above described, this big acromion is 

 present on both sides, but, peculiar to relate, it is in each only joined 

 to the main part of the spine of the scapula by a fibro-cartilaginous 

 ligament, and no crepitus is felt on moving the one part on the other. 

 If this condition is not the result of injury, which it does not seem 

 to be, it is very abnormal. 



The peculiarities of the skull make me inclined to place Aulacodus 

 nearest to Lagostomus and the American Porcupines, the former of 

 which it very closely resembles in the arrangement of the zygomatic 

 arch and palate, though the teeth present considerable difference. 

 The caecum of Lagostomus appears to be in many respects similar ; 

 but the liver is less complicated, possessing no cystic notch or 

 fossa. 



