A Manual of Palaeontology for the Use of Students; with a General Introduction on the Principles of Palæontology Volume 2

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1889 edition. Excerpt: ...commissure (corpus callosum) connecting the two cerebral hemispheres. Feathers, moreover, are never present, and there is no syrinx or lower vocal organ, although a complete larynx is always developed in the upper portion of the trachea, or respiratory tube. It will be unnecessary in this work to make any further mention of the soft parts, but a few remarks must be made concerning the tegumentary and dental systems, and the endoskeleton; although the student must refer to other works for fuller information on these subjects. With regard to the tegumentary system, it will suffice to observe that imbricated horny scales occur in the epidermis only a the family Manida among the Edentata; and flat horny shiddi with their edges in apposition, in the tails of the Beaver, Rats, m certain Insectivores and Marsupials. The Armadillos and Glyptt donts develop, however, a series of bony scutes articulating wid one another in the true dermis, which are covered by homy epi dermal shields; the whole structure being thus precisely comparablf to that obtaining in the Crocodilia. Smaller separate bony scutd also occur in the dermis of Mylodon. The horns of the Ruminant and Rhinoceroses are entirely epidermal structures; the forma being hollow sheaths enveloping bony cores, while the latter an solid throughout. The dental system, as being of extreme importance for the determination of the extinct forms, must be noticed somewhat more fully. Calcified teeth are developed in the great majority of Mammals, bu in the true Whales they occur only in the embryo, in Ornithorhyrukui they disappear in the adult, while in Echidna, Manis, and Myntt cophaga, no traces of them have as yet been detected. In the adult of Ornithorhynchus and Rhytina the function of teeth is...