11 



Anterior view (Fig.6): The head is armed with one or two teeth and a long concave 

 projection which surrounds the postero-proximal corner of BScA. The ventral tooth is 

 referred to as FScl and the dorsal as FSc2. The teeth are usually separated by a ventral 

 projection and an embay ment. 



FScl is formed as a convex tooth w hich extends along the ventral margin of the ventral 

 projection. FScl articulates in a groove formed between two large convexities on the 

 proximal margin of BScA and is prevented from pivoting anteriorly by the dorsal margin 

 of BScA. 



The ventral projection, a slender, concave structure, articulates with the inner surface of 

 the posterior convexity on the proximal margin of BScA. A concavity, which is of variable 

 length, runs the length of the ventral projection. The embayment separates FScl/ventral 

 projection from FSc2 ? and surrounds the most posterior convexity on the proximal margin 

 of BScA. FSc2 is formed as a slender, convex tooth. It articulates in a deep concavity 

 formed along the posterior margin of BScA. 



Second Axillary (2Ax). 



The second axillary is composed of the medial axalare and radial fulcalare (AXM + FR) 

 (Figs.2b. 3b. 7a). The bulk of 2 Ax is formed by AXM (Fig.7a). 



Dorsal view (Figs. 2b, 3, 7): FR. the arm. connects with the posterior radial basivenale 

 (BRP) (Figs. 2b. 3) anteriorly and AXM posteriorly (Figs. 2b. 3, 16). FR may be very large 

 and strongly sclerotized (Figs. 2b. 3. 16), slender (Fig. 7a) or absent. 



AXM is a bi-lobed structure (Fig.7). It is composed of a dorso-proximal lobe (d-pl), a 

 dorso-distal lobe (d-dl). a dorso-proximal ridge (d-pr) and a dorso-distal ridge (d-dr) 

 (Fig. 7b). The ridges and lobes are collectively termed the arm and body respectively. Each 

 lobe is generally either deltoid- or harp-shaped. The ridges extend between and separate 

 the lobes. Anteriorly and posteriorly, one ridge may conceal another. Medially the ridges 

 are often separated by a medial groove (mg) (Fig. 7c) which articulates with the lAx distal 

 embayment and arch. Anteriorly the ridges may be very long or short, strongly or weakly 

 elevated, but they always articulate with the lAx distal embayment and arch. Posteriorly 

 the ridges are broadly separated from their ventral components to form a concavity to 

 accommodate a tendon (see below). The proximal lobe and ridge are concealed under lAx 

 in intact specimens leaving only the distal ridge and lobe visible (compare Fig. 3, an intact 

 wing articulation, with Fig.7, a dissected 2Ax). The proximal lobe articulates with the lAx 

 ridges. Distally, the distal lobe is broadly fused to the medial plate (MED) (Fig. 3b). The 

 distal ridge and lobe articulate with FR (Fig. 7a). 



Ventral view (Fig. 8): Both lobes and ridges have ventral components. For convenience the 

 prefix ventro- is added. It is composed of a ventro-proximal lobe (v-pl), a ventro-distal 

 lobe (v-dl). a ventro-proximal ridge (v-pr) and a ventro-distal ridge (v-dr). 



The proximal lobe is equipped with a convexity. This convexity is termed the posterior 

 wing process junction (PWP) and articulates with the posterior wing process by a short 

 section of tough membrane. 



