TRIBE ASPIDIOTINI 383 



segments are for the most part creseentic in outline which permits 

 of their being telescoped together and the pygidium drawn into the 

 cavity formed at their caudal end. Their lateral margins are not 

 or only rarely prolonged and do not bear lateral groups of bracteae 

 or plates as is so characteristic of many mytilaspids, diaspidids, and 

 parlatorids. 



The preabdomen and pygidium are usually distinctly sep- 

 arated. The pygidium is generally provided with a pygidial 

 fringe that is typical in form and arrangement. The triangular 

 shape of the pygidium is also characteristic. The maximum num- 

 ber of pairs of lobes appears to be four, there are frequently only 

 two or three and in a number of species there is only a single pair. 

 Those species transforming in a puparium, as Aonidia, not only 

 lack lobes, but are generally provided with pseudolobes. A few 

 species not transforming in this way also lack all indication of a 

 pygidial fringe and have the pygidial margin entire. When more 

 than one pair of lobes is present, the lobes located cephalad of the 

 median pair are usually much smaller than the median pair. 

 These cephalic lobes vary greatly in shape and size and often 

 resemble the latadentes found in other tribes. The caudal margin 

 of the pygidium is only rarely concave or provided with a pygidial 

 incision with the median pair of lobes located in the incision. The 

 lobes are either notched or entire, rarely crenulate or serrate. 

 The second pair of lobes and those cephalad of them are only 

 rarely incised to form two or more lobelets of each lobe. The 

 median lobes are usually much closer together than in Lepidosaphes 

 or Chionaspis, frequently subadjacent, the median incisura is very 

 narrow, but only rarely are the lobes fused to form a single mesal 

 lobe. 



The margin of the pygidium typically bears pectinae and 

 plates or both. The pectinae vary greatly in the number and 

 arrangement of their teeth or pectinations. The simplest type, the 

 distapectinae, are sometimes found cephalad of the median pair of 

 lobes, but probably more often between this pair of lobes where 

 with specialization they become reduced to bifurcate furcapectinae. 

 The number of species provided with latapectinae is not great, 

 while there are many provided with unapectinae. The pectina- 

 tions are usually situated on the side away from the median pair 

 of lobes and are sometimes long and slender, at other times are 

 longer than the central axis of tlie pectina in the unapectinae. 

 These pectinae are of common occurrence in the incisurae cephalad 

 of the median pair of lobes and upon the lateres. Furcapectinae 



