Part 128

104. =Instep=, or =Front of tarsus= (Acrotarsium). The anterior face of the tarsus, usually covered by small plates, which in the higher groups are united into one; sometimes covered by skin.

105. =Side of tarsus= (Paratarsium).

106. =Back of tarsus= (Planta tarsi). Homologically the =Sole= (Planta).

107. =Heel= (Calcaneus; Talus). The upper posterior extremity of the tarsus.

108. =Spur= (Calcar). Any bony sharp process or spine implanted on the tarsus, as in the rooster.

109. =Scutellæ= (Scutella). The succession of small, usually rectangular plates, applied against the anterior face of the tarsus, and the upper surface of toes. These sometimes encircle the tarsus completely, meeting on the inner side; sometimes reach half round with similar half-rings on the back side of the tarsus; are sometimes divided into polygonal plates; are sometimes fused into a continuous plate, either anteriorly or laterally. Modifications of structure in this respect indicate differences in rank and systematic position of the highest value.

110. =Scutellate tarsus.= When the tarsus is covered with transverse or polygonal scales, as described above.

111. =Booted tarsus.= Where the anterior face is covered with a continuous horny plate not divided into scutellæ.

112. =Foot= (Pes). The toes and tarsus taken together.

113. =Top of foot= (Acropodium). The entire upper surface of the foot.

114. =The track= (Pelma). The entire lower surface of the foot.

115. =Heel pad= (Pterna; Tuber). The posterior portion of the pelma, immediately under the joint of the foot, and frequently prominent.

116. =Toes= (Digiti). The, usually four, sometimes three, very rarely two, articulated portions of the leg hinged on the lower extremity of the tarsus. When all four are present, one is usually behind, sometimes two before, and two behind.

117. =Top of toes= (Acrodactylum). The upper surface of the toes individually.

118. =Soles of toes= (Hypodactylum). The lower or plantar surface of the toes individually.

119. =Side of toes= (Paradactylum). The sides, in any way distinguished from the soles.

120. =Phalanges.= The several bones composing a toe.

121. =Claw= (Ungues). The horny tips sheathing the last joint of the toes.

122. =Claw joint= (Rhizonychium). The terminal bone of the toe, carrying or armed with the claws.

123. =Pads= (Tylari). The swellings or bulbs on the under side of the phalanges. Those =Toes= are

124. =Anterior= which are directed forwards;

125. =Posterior=, directed backwards;

126. =Exterior=, on the outer side of the foot;

127. =Interior=, on the inner side of the foot; the

128. =Middle toe= is the central of three toes directed forwards.

129. =Hind toe= (Hallux). The single toe directed backwards. This is homologically the first or great toe directed backward. It is

130. =Insistent= (insistens), when the tip at least touches the ground, but the base raised above the level of the rest;

131. =Incumbent= (incumbens), when its whole under surface touches the ground; and