230 THE COCCIDAE 



groups; in the first group they are broad, the distal end is trun- 

 cate or subtruncate and the teeth are limited to the distal end. 

 These are the distapectinae and are of general occurrence in the 

 Parlatoriini. In the second group the shaft may be comparative!}' 

 broad or narrow, the distal end is pointed, so that each pectina 

 is subtriangular in outline and the teeth are arranged along both 

 sides of the shaft. These are the latapectinae. In the third 

 group the pectinae are similar in size and form to those of the 

 second group, but the teeth are limited to one side of the shaft. 

 These are the unapecthiae. The fourth group includes those pec- 

 tinae in which there has been the greatest amount of reduction, 

 those with a slender shaft with two or three small inconspicuous 

 teeth at the distal end. These are the furcapectinae and are gen- 

 erally indicated as furcate plates by systematists. The latapecti- 

 nae, unapectinae, and furcapectinae are all found in the Aspidi- 

 otini. 



The thin cuticular projections with pointed ends located in 

 the incisurae between the lobes are the plates. They are also 

 known as lamellae, gland spines, spine ducts, fusi piliformis, or 

 fusi spiniformis. The plates are considered as having been de- 

 veloped from pointed pectinae by the loss of their lateral pro- 

 jections or teeth. They are similar in number and position to the 

 pectinae and like them each bears an oraceratuba at its distal 

 end but it is generally more difficult to identify the oraceratuba 

 than the cylindrical part of the ceratuba extending through the 

 icavity of the plate. If the plates and pectinae are continuations 

 'of the margin of the pygidium, each is typically provided with 

 a lumen which is a continuation of the lumen of the body. The 

 plates are frequently minute and often difficult to distinguish 

 *rom setae, the spines of most authors. It is not strange, there- 

 tore, that they have been sometimes confused with setae, but they 

 can always be distinguished from setae by the absence of a calyx. 



The number of plates and pectinae located in each of the 

 incisurae is of great value in the separation of species. Cooley 

 has suggested that for the sake of brevity the number of plates 

 be indicated in the form of a formula, but this scheme is just 

 as serviceable in indicating the number of pectinae. The for- 

 mula is written, as follows : 1-0, 1-2, 3-3, 1-2, 2-2, 3-7. The first 

 group of numbers shows the number of plates or pectinae in the 

 median incisura, the cypher indicating their absence, the second 

 group those of the second incisura, the third group those of the 



