|;;| SAMUEL H. SCUDDEK ON THE 



individuals, the extremes of which may again be represented in tigs.5and9; in the former 

 of these the basal abdominal segments arc only about half as broad again as long, and 

 the middle ones arc about square; while in the latter, the basal abdominal segment is 

 more than twice as broad as long and it is only the terminal segment which is square. 

 A- a very general rule, the segments are quadrate, with very gently convex sides, and 

 slightly and equally rounded anterior and posterior lateral angles; but in a lew cases, as 

 in I'm'. !*, the anterior angles are considerably more rounded than usual, and the posterior 

 angles, besides being square, are furnished with a faint posterior extension, bristle, or 

 tapering- cluster of hairs (it is impossible to say which, but the last is the most probable). 

 This same posterior set of appendages maybe seen more or less distinctly in some of the 

 other specimens, where the segments have the posterior angle as rounded as the anterior, 

 but otherwise resemble this fig. 9 (as in tig. 1), or in which the segments are of the nor- 

 mal form, as in fig. 6, which represents the specimen which apparently furnished the 

 figure which has hitherto been current, and in which these appendages appear more 

 decidedly as hairs, being more spread out, and also as attached to the posterior thoracic 

 segments. 



The surface of the abdominal segments is in general flat, but not quite uniform, at 

 least on many specimens. There appear to be two kinds of inequalities, one of which 

 from its infrequency and position seems to be accidental, perhaps due to pressure. This 

 is seen in iig. 1G, in sharp lines close and parallel to the margin. The other, however, 

 though often obscure, is too common to be so considered, and consists in a longitudinal 

 series of slight ridges, laterally convex, and extending the whole length of the abdomen, 

 dividing the segments into equal or subequal transverse thirds, of which the middle 

 third is apt to be the largest. This may be seen in figs. 1, 6, 15. Besides these, there 

 is nearly always some median mark of greater or less intensity, indicating probably the 

 track of the alimentary canal. Two specimens which I have figured (figs. 2, IT) show 

 this in a marked degree, the remains of a tube which extended the entire length of the 

 body being visible. It is much more pronounced on the abdominal segments than else- 

 where, but in Iig. 2 more distinct on the anterior half of the abdomen, while in fig. 11 it 

 is more distinct on the posterior half, where it is clearly at least double, being turned 

 upon itself between the fifth and sixth abdominal segments, forming there a distinct 

 rounded loop, and again more obscurely on the front of the eighth segment. To cor- 

 respond with this, we have in tig. 2 a distinct horse-shoe shaped depression superposed 

 a little laterally on the median groove at the posterior end of the fifth abdominal seg- 

 ment, and a shallower, smaller, circular depression in which the groove appears to ter- 

 minate on the front of the seventh abdominal segment. From these it would appear 

 tolerably clear that a slender alimentary canal, nowhere expanding into a well marked 

 stomach, doubled sharply upon itself at or near the seventh abdominal segment, and 

 again, by doubling at the hinder extremity of the fifth abdominal segment, resumed its 

 former course, the whole of the sixth segment and at least a part of the seventh having 

 therefore three sections of the canal passing through the middle. 



The variations in form of the different segments of the abdomen have been mentioned. 

 It now remains to speak of the curious variations of the terminal or ninth abdominal 

 segment and of its special appendages. The general relation of this segment to the 



