Mr. A. Tulk on the Anatomy o/Phalangium Opilio. 161 



and scmicyliudi-ical bow (PL III. fig. 10. n) is perceived. It 

 commences by a pointed extremity, which is continued from one 

 of the external folds, and runs almost parallel with the anterior 

 margin of the second pair of jaws, bending as it approaches the 

 median line, and passing upwards towards the under sm-face of 

 the epipharjaix, this vertical part of its course being about twice 

 the length of the preceding, or transverse. When at some depth 

 above the under sm-face of the body, this bow bends again sud- 

 denly upon itself in the chrection upwards, the convexity formed 

 by the loop being placed most external, and narro^^ing and be- 

 coming flattened as it proceeds obliquely upwards and inwards, 

 terminates by blending with the free border of the folded mem- 

 brane of the jaws. Within the concavity formed by this bow 

 may be seen the rounded extremity of the elongate piece (PI. III. 

 tigs. 9 and 10. o) mentioned in speaking of the maxillary palpi, and 

 with which the bow is connected by a thin membrane externally, 

 while on the opposite side it is continuous with that of the jaws. 

 After it has reached, however, the loAver border of this piece, it 

 curves round it, and is then simply supported by the free and 

 delicate margin of the maxillse (PI. III. fig. 9. p). This latter, 

 thickened and cartilaginous for about half its extent, forms an 

 angle superiorly {q) with that portion of the maxilla which is 

 continuous with the margins of the labrum, and projecting in 

 the middle triangularly, becomes very thin and membranous, and 

 where the terminal part of the bow rests upon it, is prolonged 

 upwards in an obtusely angular 'manner. The bow itself is formed 

 by a simple eflection of the maxillary membrane, and its cyhnder 

 is incomplete inferiorly, where the margins coalesce with the 

 latter. The dark colom- of the anterior plicated portion of the 

 maxiUse is due to the presence of numerous brown, closely ap- 

 pressed hairs, which are longest upon the middle of the folds, 

 and have an obhque direction upwards. They are seated upon 

 short and parallel ridges, and give a pecidiarly soft and velvety 

 appearance to the jaws. 



As the first pair of jaws were found to be formed by internal 

 prolongations of the basal joints of the palpi, which were in 

 themselves, essentially, modified organs of locomotion, so the 

 second, or succeeding pair of maxillse, placed immediately behind 

 them (PI. III. figs. 3 and 8. B), occupy a similar position in relation 

 to the first pair of coxpe (1, 1), and, though simpler in construc- 

 tion, yet consist, hke the preceding, of two membrano-coriaceous 

 pouches, which, when distended by fluid, present a very regular 

 and oval form. Attached to the anterior side of the inner ex- 

 tremity of the coxse of the first pair of legs is a short and longi- 

 tudinal ridge of integument (Pl.III. fig. 12. a) with a few bristles 

 upon it, terminating in front by a free, slightly curved and ob- 



