i4 THE ANATOMY OF VERTEBRATED ANIMALS. 



have bony dermal plates con-esponding in foi-m and size 

 witli the epidermal scales. All Crocodilia liave such bony 

 plates in the dorsal region of the body and tail ; and in some, 

 such as the Jacares and Caimans, and the extinct Teleo- 

 sauria, they are also developed in the ventral region. In 

 these animals there is a certain coiTespondence between the 

 segments of the esoskeleton and those of the endoskeleton. 

 But the dermal exoskeleton attains its greatest develoj^ment 

 in the Chelonia, and wiU be particvdarly described under the 

 head of that order. 



In the Mammalia the development of a dermal exoskele- 

 ton is exceptional, and occurs only in the loriea^ted. Edentata, 

 in which the dorsal region of the head and body, and the 

 whole of the taU, may be covered with shields of dennal 

 bone. 



In connection with the dermis and epidermis, the glan- 

 dular and pigmentary organs of the integument may be 

 mentioned. Integumentary glands do not appear to exist 

 in Fishes, but they attain an immense development in some 

 of the Amphibia, as the Frog. Among Beptilia, Lizards fre- 

 quently present such glands in the femoral and cloacal 

 regions; and, in Crocodiles, integiimentary glands, which 

 secrete a mxisky substance, lie beneath the jaw. In Birds 

 they attain a considerable size in the uropygial gland ; and, 

 in Mammalia, acquire a large development in connection with 

 the sacs of the hairs, or as independent organs, in the form 

 of sweat-glands, musk-glands, or mammary glands. 



The colour of the integument may arise from pigment- 

 granules, deposited either in the epidermis or in the 

 dermis ; and in the latter case, it is sometimes contained in 

 distinct chromatophores, as in the ChamcBleon. 



