PROC. ENT. SOC. WASH., VOL. 24, NO. 1, JAN., 1922 17 



The anterior foramen of the notum is regularly and trans- 

 versely elliptical, except for the more strongly arched margin 

 of the sternum and the anterior excavations of the sterno- 

 pleural sutures. In fissilis Say the posterior foramen of the 

 pronotum (fig. 15) has the superior margin strongly arched and 

 very sinuate, being brought down on the sides to meet the 

 posterior margin of the fused pleura and the inflexed part of 

 the notum at a point about midway between the apex of the 

 posterior angle and the juncture of the pronotal-epipleural 

 margin with the coxal cavities; this superior margin of the 

 foramerr is strongly reentrant just before attaining the lateral 

 margin. The sides of the foramen are strongly convergent 

 ventrally but are separated below by the coxae and the mucro. 

 Above the superior margin of the foramen, and meeting it only 

 along the middle, is the transverse posterior margin of the 

 plane of the notal disc, extending between the posterior angles 

 and bearing the sulci. This leaves on either side of the center 

 and above the posterior foramen, a roughly triangular, deeply 

 excavate area bounded by the superior margin of the foramen, 

 by the posterior margin of the plane OF the disc of the notum 

 and by the exterior half of the posterior margin of the pronotal 

 epipleura or tergo-pleural region. 



The sternum of the prothorax throughout the genus is convex 

 and longitudinal, with the sides subparallel as far as the coxae 

 (St 1, fig. 16, M. fissilis Say). Anteriorly it is broadly rounded 

 and more or less deflexed, depending upon the species, to form 

 a vague lobe (PtL, fig. 16) whose free margin is finely raised. 

 On either side the sternum is bounded by externally concave, 

 .double sterno-pleural sutures (Sps, fig. 16) which are somewhat 

 widened and excavate anteriorly. Posteriorly these sutures 

 curve outward and the inner of them ends in a small pit near 

 the anterior edge of the coxal cavity. The outer suture con- 

 tinues backward, passing around the coxal cavity and finally 

 disappearing in the general direction of the posterior angle as 

 a vague sinuate line more or less parallel with the posterior 

 margin of the pronotal epipleura. 



Posteriorly the sternum of the prothorax is sharply narrowed 

 by the coxal cavities to form the prosternal process or mucro 

 (figs. 13 & 16). \\-\fissilis Say the mucro is slightly concave 

 between the coxae, with its lateral margins somewhat rolled; 

 along the posterior third of the coxae the mucro becomes 

 gently declivous, at the same time narrowing more sharply on 

 its ventral than on its dorsal face; its tip is slightly declivous, 

 forming a blunt apical point which curves gently toward the 

 body. 



Between the sterno-pleural sutures and the lateral margin of 

 the notum lies a wide area, the proiiotal epipleura or tcrgo- 

 pleural area (PE, fig. 16) which is composed of the inrlexed 



