REPORT OF THE STATE PALEONTOLOGIST 1902 1093 



I 



The second segment is twice as long as the first, its posterior 

 edge is slightly concave along the middle portion, and the 

 posterior angles are rounded, while the anterior are produced, 

 to make up, as it were, for the rounding away of the preceding 

 tergite. The succeeding tergites are very nearly equal in 

 length, the fifth being perhaps a little the longest, and are 

 about one third longer than the second. The posterior margins 

 are concave as in the preceding, but straighter near the sides,, 

 forming almost right angles. 



The first ventral plate, or sternite (the operculum), is 

 one third as long as broad, and is divided along the axial 

 line into two equal parts. \ These are rounded off at the lateral 

 angles, particularly the anterior, and excavated along the median 

 line for the reception of the opercular appendage; the posterior 

 edges are slightly projected on either side of this, while the- 

 anterior inner angles are projected forward, forming a com- 

 pound median lobe. The second sternite, in the female, is nearly 

 as long as the operculum, and is deeply cleft for the reception 

 of an appendage nearly equal to it in length. The sides are cut 

 obliquely forward, making the posterior angles rather acute;: 

 the anterior angle forms small lobes, and the middle of the 

 anterior edge is slightly produced. In the male the last four 

 sternites, and in the female the last three, do not differ mate- 

 rially from the last four and three abdominal tergites. The 

 relative position of the several plates of the sternal series to 

 those of the tergal, is as follows: the opercular plate begins 

 a little farther forward than the first tergite, but, owing to its 

 greater breadth, lies beneath the line of overlap of the first and 

 second tergites, while the second sternite lies beneath the over- 

 lap of the second and third tergites, and so on, the last sternite 

 underlying the overlap of the fifth and sixth tergites, thus not 

 extending as far back as the posterior edge of the sixth tergite. 



Fostabdomen. The first postabdominal segment consists ol 

 a tergal and a sternal portion united by their appressed' 

 pleural ends. The postlateral angles are prolonged into short, 

 bladelike lobes which extend alongside the following segment 

 for fully half its length. The tergal portion is the longer,. 



