Rev. F. D, Morice un Armatures, etc. of Andrena. 233 



But when extracted properly it is a pretty and interesting 

 microscopic object, though less so than the 8th. [Plate V, 

 Fig, 1, shows the 7th segment in A. coitana, Kirby (a) 

 and lahialis, Kirby (b) ; Fig. 2 {himaculata, Kirby) shows 

 the 7th segment (white) lying inside the 6th (shaded) ; 

 Fig. 8 (also himaculata) shows the 7th segment (white) 

 crossing the 8th (shaded).] 



We can now turn to the specific characters of the 

 stipitcs (Plate V), and the valvula vcntralis (Plate V, VI, cf. 

 also Plate VII illustrating the next paper). To define 

 them a few technical terms will be required, which I will 

 try to explain as shortly as possible by reference to my 

 figures. Some have been used already, but I will enu- 

 merate them all together here. 



In Plate V, Fig. 4a, a single lobe (morio) is shown 

 diagrammatically with explanatory lettering. Thus d c ef 

 is the ' lobe of the stipes,' g ahh is its ' process ' ; c d 1 

 call the 'apical outline' of the lobe, dc,cf,fc, its 'in- 

 terior, basal, and exterior ' outlines respectively ; cde (the 

 inclination towards each other of the apical and interior 

 margins) I call the ' angle.' In Fig. 6 the apical margin 

 may be called ' straight,' in Fig. 19 it is ' strongly sinuated 

 inwards,' in Fig. 15 it has a ' strong S-like sinuation.' In 

 Fig. 6 the lobes are quite ' adjacent,' in Fig. 10 they are 

 only adjacent at the base, in Fig. 11 they are ' separated 

 at the extreme apex.' 



The angle at d in Fig. 4a is ' practically a right angle,' 

 in Fig. 6 the corresponding angle is ' acute,' in Fig. 9 

 ' obtuse ' ; in Fig. 21 it is ' narrowly dentate,' in Fig. 22 

 ' widely dentate,' in Fig. 15 it is ' rounded o&;' ahh is the 

 ' exterior outline ' of the process, g c its ' interior outline ' 

 (gi is a, part of the posterior margin of the stipes, and 

 may generally be disregarded). 



Of course the appearances of these outlines will vary 

 when the position of the segment is shifted. It is highly 

 necessary, therefore, in comparing two armatures to get 

 them into the same position. It must be remembered that 

 these outlines are not all true margins, but rather ' hori- 

 zons,' produced by the convexity of the stipes. Still, their 

 diiferences of appearance in the various species are very 

 constant and characteristic. 



In Plate VI the ' basal plate ' and ' process ' of the 8th 

 segment will be easily recognised in most, if not all, of the 

 * ventral views,' e.g., Fig. 4 shows them in a very simple 



