NO. 13 STAPHYLINIDAE — BLACKWELDER I9 



notal sutures (sns). The lateral and caudal margins are occupied 

 by a fine ridge or thickening (mm), which, near the anterior lateral 

 angles, passes onto the ventral aspect and disappears. The area set 

 off by the marginal ridge is known as the hypomera (hypo) or the 

 inflexed part of the pronotum. The dorsal surface of the pronotum 

 is moderately convex, nearly quadrate with the angles broadly rounded, 

 and very slightly wider than long. The broad median area is smooth 

 and even on the surface, but it is traversed by numerous fine canaliculi, 

 which appear to be larger and more definite in arrangement than the 

 usual irregular canals in sclerotized integuments. Each canal ends at 

 the surface in a minute puncture which appears to bear an extremely 

 fine and short point or setula. The sides of the dorsal surface are 

 beset with moderate setae which are set in large punctures. This area 

 is continued at the anterior corners onto the lateral and ventral aspects 

 by the continuation of the marginal ridge. 



The hypomera is itself slightly deflexed along the margin of the 

 coxal cavity, and this deflexed part is set off by a rather definite line 

 which extends posteriorly for some distance. Just caudad of the 

 coxal cavity and nearly over the mesothoracic spiracle, this deflexed 

 part is expanded medially into a membranous lobe (fig. 3 A, prnl, C) 

 which partially closes the cavities behind. Its anterior edge is densely 

 covered with very fine membranous processes (figs. 3 C, D) of two 

 types. Single slender and finely pointed processes occupy the greater 

 part of the area, and shorter fimbriate groups of five to seven points 

 occur in a band around the margin. These groups and the single 

 points are connected in series by fine folds of the surface and appear 

 to be merely expansions of these folds. The posterior parts of the 

 hypomera bear no setae but have many of the fine canaliculi on the 

 lateral portions. 



The ventral aspect of the prothorax is occupied by the sternum, 

 the hypomera, the coxal cavities, and the anterior and posterior 

 foramina, which receive parts of the head and mesothorax respec- 

 tively. A considerable caudal area is membranous, and one sclerite 

 (fig. 3 A, peri) lying in this area belongs to the mesothorax. This 

 is the sclerite that bears the so-called prothoracic spiracle (sp), which 

 is undoubtedly morphologically a part of the mesothorax. 



The presternum is composed of two sclerites, the basisternum 

 (fig. 3 A, bs) and the furcasternum (fs), separated by a suture 

 (stcs) , the sternacostal suture. The basisternum is a transverse sclerite 

 along the ventral or posterior border of the anterior foramen (afor), 

 extending laterally to the notostemal suture (sns) and forming the 



