OF THE UNITED STATES 141 



turnal varieties, while as a rule they are stationary by prefer- 

 ence, remaining long in any particular locality, or as long as the 

 food in it is plenty. In them the action of the ribs lakes the place 

 of limbs, and constitute their organs of locomotion, the various 

 movements of snakes being a very interesting study. These 

 movements consist in their action upon the ground, in the water, 

 in trees; in their modes of attack; in their fighting each other, 

 and in copulation, ovulation, and the struggles of death. As 

 with other vertebrates, snakes are classified in accordance with 

 their anatomical structure and habits. Many of the structural 

 characters found in snakes are worthy of the closest study. For 

 example, the difference between the dental armature of a truly 

 venomous snake and an innocuous one is very characteristic. 

 The pattern of the tooth-marks, when the teeth of either kind are 

 driven into the flesh, are distinctly different. In the case of a 

 poisonous snake, we note the two roughly parallel rows of cen- 

 tral teeth, while in front, upon either side of these, the row of 

 two or three punctures made by the poison fangs. These last 

 two rows of wounds are parallel to each other. Now, the two rows 

 of central tooth-punctures in a harmless snake are similar to 

 those of a venomous one, but the difference occurs in the lateral 

 or outside rows. They are long and curved, the curves corre- 

 sponding to those of the upper jaw of the reptile, the entire mar- 

 gin of which is usually armed for its whole length by a long, 

 single row of minute teeth upon either side, but the rows not 

 meeting in front. Then, again, there is that interesting struc- 

 ture, the "rattle" of the rattlesnake, and upon this an authority 

 at hand has said: "The bone by which the root of the rattle is 

 supported consists of the last caudal vertebra?, from three to 

 eight in number, which are enlarged, dilated, compressed, and 

 coalesced. This bone is covered with thick and vascular cutis, 

 transversely divided by two constrictions into three portions, of 

 which the proximal is larger than the median, and the median 

 much larger than the distal. This cuticular portion constitutes 

 the matrix of a horny epidermoid covering which closely fits the 

 shape of the underlying soft part, and which is the first com- 

 mencement of the rattle, as it appears in very young rattlesnakes 

 before they have shed their skin for the first time. When the 

 period of a renewal of the skin approaches, a new covering of the 

 extremity of the tail is formed below the old one, but the latter, 

 instead of being cast off with the remainder of the epidermis, is 



