STRUCTURE OF LERNEOPODA DALMANNI. 79 



laterally close to the angles of junction of the lips. They lie obliquely across the 

 cavity, and therefore cross each other. In some of the specimens the free 

 ends of these mandibles projected externally through the oral aperture (fig. 7). 

 Deeply serrated strong teeth, about six in number, with intermediate smaller 

 teeth between the three terminal ones, are placed along the concave posterior 

 margin of the unattached extremity of each jaw. Each mandible is articulated 

 externally to the chitinic plate which supports the lips. The muscles which move 

 the jaws do not present any distinct transverse striation. They are marked by 

 delicate longitudinal striae, which resemble nuclei in their appearance. 



Connected laterally to the outer aspect of the upper lip is a very small pro- 

 jecting structure, which Kroyer has described as a touch organ, and which 

 may evidently be considered to be a labial palp (fig. 8, a). It consists of two 

 segments, from the terminal one of which three papilla-like hairs project. The 

 basal segment has, along its line of articulation with the terminal, a short hook- 

 supporting tubercle, and from its outer surface, about half way towards the base, 

 there is an elevation fringed with very short bristles. 



The stump-like processes, between which the snout, bearing the mouth, lies, 

 have been termed by Kroyer the second pair of antennse (fig. 6, d, fig. 10). 

 They correspond very nearly, both in structure and relation to the mouth, to the 

 appendages which V. Nordmann has described and figured in Achtheres percarum 

 as the upper jaws, or metamorphosed first pair of feet. Each of these structures 

 is segmented and laterally compressed, and arises b}'^ an elongated base, which is 

 not merely on the same line with the base of the snout, but extends forwards 

 beyond it for a short distance towards the anterior extremity of the cephalo-thorax. 

 Each possesses a bifid free extremity, the posterior division of which, smaller than 

 the anterior, is armed with a well-marked terminal hook. Along its posterior 

 margin are two elevations, studded with short, blunt, cylindrical bristles (fig. 10, 

 a). Immediately above the lower of these elevations is a smaller space covered 

 with conical hairs. The anterior division, very much larger than the posterior, 

 is thickly studded, especially on its outer surface, with a corresponding bristle- 

 like arrangement (fig. 10, b). Springing from the anterior and inner part of each 

 of these modified feet is a segmented palp-like structure, set with three or four 

 conical papillae at its free extremity (fig. 10, c). 



At the inferior margin of the anterior extremity of the cephalo-thorax is a 

 somewhat pendulous nipple-like structure, which has been named by Retzius the 

 chin (figs 4, b). It consists simply of a projection of the integument, which can 

 be retracted or protruded at pleasure. 



A pair of elongated cylindrical arms arises from the sides of the cephalo-thorax 

 immediately in front of the constricted neck (fig. 1, c). When fully extended, 

 each arm measures an inch, but it can be contracted by the animal at least one-half. 

 The arms pass almost vertically upwards in the direction of the long axis of the 



