NEW MALLOPHAGA. 149 



structures, attachetl to tlic head l)y a condyle on one 

 side ami a socket on the oi)[)Osite side of the outer basal 

 angle. From the inner angle of the base a prolongation 

 extends inward. The two teeth project from the inner 

 edge, generally one distal to the other. The mandibles 

 present two modifications, one found in the Amljlycera 

 and the other in the Ischnocera. In the former they 

 lie parallel with the ventral surface of the head, so that 

 the condyle is ventral and the socket dorsal. In this 

 form one tooth lies in front of the other in a horizontal 

 line in the same plane as the long axis of the mandible. 

 In the Ischnocera the mandibles hang vertical to the 

 head, so that the condyle is posterior and the socket 

 anterior. In this form the distal tooth is typically 

 ventral to the other in a vertical line in the same plane 

 as the long axis of the mandible. The more proximal 

 tooth, however, may be moved toward the tip and come 

 to lie by the other and in front of it (plate x, fig. (3). 

 lu this case the two lie in the same horizontal line, 

 but this is perpendicular to the long axis of the mandi- 

 ble. Starting with either typo, the other may be pro- 

 duced from it by revolving the mandible on an axis 

 passing from its outer to its inner basal angles. The 

 degree of revolution varies in different Ischnoceran spe- 

 cies, but the angle is always hirge and may reach 90"^. 

 In many cases there is a chitinous plate or rod attached 

 to the inner angle of the base of the mandible, and a 

 smaller one attached to the outer. These serve for 

 attachment of muscles (plate x, fig. 12, <•/*. j>ls.) extend- 

 ing backward or upward into the head cavity. When 

 they are absent muscle fibers are attached directly to 

 the mandibles. 



The maxilla^ are generally simple, small, non-chit iu- 

 ized lobes, often provided with teeth on their inner 



