HELIOMETRINAE 139 



be faint or exceedingly strong: they are faint when the axillary and second brachial are 

 broad and short, strong when they are elongated (compare a^ and a^). The partial lateral 

 apposition of the costals referred to above appears to come about only in those old 

 specimens in which the axillaries are comparatively wide and form a faint, or no, 

 shoulder with the costals. 



The first syzygy is between the third and fourth brachials ; the second and third are 

 usually between the ninth and tenth and fourteenth and fifteenth respectively, though 

 irregularities occur. The syzygial pairs beyond the third are separated by one to five, 

 usually two or three, brachials. 



The brachials between the first and third or fourth syzygies are rectangular or 

 quadrate, usually broader than long, but sometimes as long as broad or even slightly 

 longer than broad. Beyond the third or the fourth syzygy the brachials are triangular 

 or wedge-shaped, broader than long or as long as broad. The distal brachials are rect- 

 angular, as long as or longer than broad. The brachials of young specimens are pro- 

 portionately longer than those of older specimens. 



The lower brachials may be smooth or spiny ; the distal edges of the outer brachials 

 are nearly always slightly raised and produced into spines. The brachials between the 

 first and second syzygies may have more than the distal halves of their dorsal surfaces 

 raised into rectangular patches of strong spines standing out at right angles to the 

 surface, conspicuous in profile (Fig. 2 b) ; the patches become smaller in area and more 

 triangular in shape between the second and third syzygies; beyond the third syzygy 

 they become reduced to a row of strong forwardly directed spines along the distal edge 

 of the segment, and they persist as such to the end of the arm. The spine patches of the 

 lower brachials may be smaller and of a diff'erent shape, and they may not start till the 

 sixth or seventh brachial or beyond, and the spines of the outer brachials may be 

 correspondingly smaller ; or the lower brachials may be quite smooth and those beyond 

 may have slightly produced edges which are smooth or finely or strongly thorny. 



Pi is long and whip-like, of 40-60 or, exceptionally, of up to 75 segments; it is 

 usually 15-22, sometimes as much as 26, mm. long. The first 6-12 segments are usually 

 broader than long, or as long as broad, a little stouter than the following and roughly 

 diamond-shaped. Their short and narrow dorsal surfaces may be raised into thorny 

 crests. The following segments are of a regular shape and longer but not elongated: 

 they are not so much as twice as long as broad; the more proximal may be raised 

 dorsally into a fine thorny crest. 



P2 is usually of fewer segments : those examined were of 26-46 except for one which 

 was of 62. The number is usually between five and ten less than that of Pj of the same 

 specimen. Pg is of about the same length as Pj: it may be shorter or longer. The first 

 4-5 segments are usually more massive, compared with the others, than the basal seg- 

 ments of Pi ; the others are slightly more elongated, though rarely so much as twice as 

 long as broad. 



The first genital pinnule is usually P3 or P4. P3 is commonly of 16-40, sometimes 

 of up to 60, segments. Whether it is an oral or a genital pinnule it may be of roughly 



3-2 



