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Show 1873.] ANATOMY OF AULACODUS. 789 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 vesiculee 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 membranous urethra is 3 inches long; Cowper's glands are about the size of peas, dark red and 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 m e 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. |