244 APPENDIX F. MYRIAPODS. 



The second segment is quite short, the shortest of all, and contrasts 

 strangely with the others, which preserve regular proportions, gradually 

 diminishing from the middle of the length towards both extremities, 

 with but few exceptions. The first segment or ring is one of these, 

 being the shortest after the second ; its anterior margin is subcrescentic, 

 the concavity of which receives the cephalic shield or disk (head.) 

 Besides the anterior pair of locomotory appendages, it gives a point of 

 attachment to a pair of robust and two-jointed forceps, functioning as a 

 pair of jaws for seizing and holding the prey. The central piece is 

 large and sub triangular, the anterior margin of which is denticulated, 

 (the second lip of some authors.) That second or external lip (labrum) 

 is formed by the union of two pieces, which are separate in the young, 

 where they constitute a third joint to the forceps-jaws, the second lip 

 then being also separate, and existing as a limina already denticulated 

 anteriorly. The next joint is short and stout ; the second is a conical 

 and tapering spine, curved inwardly and perforated, as it is well known, 

 for the passage of a venomous fluid, not otherwise dangerous. 



The cephalic disk itself, seen from above, is subcircular in shape, pro- 

 jecting slightly between the antennse, and showing upon its surface traces 

 of the dorsal carinse alluded to above. To its inferior surface we find 

 attached two pairs of mandibles and one pair of palpi. In proceeding 

 from outwards inwards, we will find immediately behind the forceps- 

 jaws the palpi, (little feet, sometimes called,) composed of four flattened 

 joints and a minute, curved, and terminal hook. They are united at 

 their base by the means of two additional eentral pieces. The second 

 joint is the longest, and slightly bent. The exterior pair of mandibles, 

 the one next to the palpi, is composed of four joints, the first being 

 almost as long as the three remaining ones ; the fourth is rounded, pre- 

 senting an inner concave surface with a sharp terminal margin. They 

 are united upon their middle by a lanceolated ligula. The inner pair 

 of mandibles is composed of two pieces ; the first irregularly shaped, 

 the second subcircular concave, subcircular and margined anteriorly 

 by small spines, four or five in number, constituting a denticulated 

 margin. 



In the anterior margin of the cephalic disk are inserted the antennse, 

 composed of twenty-five joints gradually diminishing in thickness, and 

 increasing in length towards the extremity, which is filiform. Exteri- 

 orly to the antennae, and close to the margin of the disk, are situated 

 the ocelli, four on each side, as usual in the genus, and disposed as rep- 

 resented in figure 5. 



