256 Transactions of the 



and where the attachment has also taken place beneath the longi- 

 tudinal rib, often a corresponding interval is noted, so that the 

 oblique markings appear to follow one another in a series of broken 

 lines: sometimes the Unes or streaks seem to pass towards the 

 central rib, as though no union had taken place when crossing the 

 long and transverse bars, though this is rarely the case. The long 

 ribs have a somewhat puckered look at those oblique junctions 

 (Fig. 19). In many scales the strong portions of the framework 

 contract towards each other, or no longer continue a jmrallel course ; 

 and where the rib gets a strongly-twisted look, supposed to be due 

 to the vertical partitions, a strong shadow is cast on one or other 

 side, according to the incident hght and position of the scale, the 

 rib itself seeming to shade off towards the obhque attachments. If 

 the transverse bars be continued, as it were, far into the substance 

 of the long rib, they give a markedly beaded arrangement. 



It is here, I think, we get a clue to the construction of the " Test 

 scale." For a very fine example of this object, I am greatly indebted 

 to the kindness of Mr. Mclntire, and from which slide the drawings 

 on Fig. 26 have been made, in the following order, after carefully 

 studying different scales. 



The Lepidocyrtus scale, in the strongly-marked examples, when 

 first focussed upon at its inner surface with high powers, shows 

 according to the illumination a series of ribs as stated by the late 

 Richard Beck, more or less continuous in their length, with faint 

 cross striae, first directly pointed out, I believe, by Dr. Pigott (Fig. 

 26, a) ; the ribs seem bent somewhat to one or other side, due it is 

 considered to the vertical attachments, so getting depressed and 

 rather twisted or narrowed as they emerge on either side, towards 

 what is seen to be with other illumination the oblique junctions 

 (" striae") to the transparent membrane, assuming an outer and inner 

 membrane at least to exist ; while these form, as it were, a broken 

 or interrupted septum between tliem, and thus being repeated at the 

 opposite side of the rib, but at a higher or lower position, we get 

 the boundary of the opposite ends, so as to embrace the heads of 

 what at a little deeper focus forms an elongated, more highly re- 

 fracting part of the scale, in which the transverse markings, which 

 correspond to the transverse bars of the Lepidoptera scale, are readily 

 seen, and iorcibly figured by Dr. Pigott (vide Fig. 26, h). The fine 

 transverse "striae" which appear at the first focus, I am inclined 

 to regard as arising from the refractions occasioned at the junctions 

 of the vertical septa, and where these alternate to right and left, 

 they give rise, as in some examples of the Lepidoptera scale 

 (Fig. 23), to a doubly-beaded appearance of the rib, with a dark in- 

 tervening shadow, seen under another focus and direction of the 

 incident light, as at i, Fig. 26. 



Still deepening the focus but retaining the same illumination as in 



