NO. 13 STAPH YLINIDAE BLACK WELDER 47 



Strip anterior to the sternal suture. The lageniform pores are very- 

 abundant, especially on the posterolateral portions of the ventral as- 

 pect of each sternite. 



The paratergites (fig. 9 A, ptt, E) are narrow longitudinal sclerites 

 on the dorsal aspect between the tergites and the up-turned edges of 

 the sternites. There is one on each side of the first abdominal tergite, 

 one on each side of the second tergite, and two on each side of the 

 segments from the third to the seventh. The eighth segment alone has 

 no paratergites. The first two segments have already been described. 

 The paratergites of the third to the seventh segments are very similar 

 in form and arrangement throughout. The median one is slightly 

 expanded and truncated anteriorly and more or less tapering caudally. 

 The outer one is rather larger posteriorly but rounded, and tapers 

 somewhat anteriorly. On the seventh segment the inner paratergite is 

 much shorter, being only half the usual length and more sharply taper- 

 ing. All the others are equal in length to the rest of the segment. The 

 inner paratergite of each segment bears a raised line or fold {pts) 

 near the anterior end in such a position as to appear to be a continua- 

 tion of the tergal suture (ts). 



The endoskeleton of the abdomen consists chiefly of narrow apophy- 

 ses along the margins of the segments. These are sometimes known as 

 plicae, and MacGillivray has proposed a system of naming them. 



Each of the dorsal segments from the second to the ninth has a 

 narrow phragma near the anterior margin which extends along the 

 sides to the posterior angles except on the second, eighth, and ninth 

 segments (fig. 5 A). These phragmata are marked externally by 

 sutures (fig. 9 A) except on the second, eighth, and ninth segments, 

 in which the phragmata are at the anterior edge of the segment. Each 

 spiracle, except those on the eighth segment, has a small roughly 

 circular apophysis on its ental surface. On the fifth and sixth segments 

 there is a very small transverse apophysis just in front of the margin. 

 These are apparently not marked on the exterior. 



The tergal or dorsal member of each pair of paratergites has a 

 narrow apophysis along the anterior end and the median edge. This 

 is found only on the third to seventh segments. 



The ventral segments from the third to the eighth each have an 

 anterior apophysis similar to the dorsum. A transverse posterior 

 apophysis is present on the third to sixth sternites. 



THE GENITALIA 



The abdominal segments posterior to the eighth form the genitalia. 

 Owing to special modifications, these are very different in the two 

 4 



