364 Prof. Allman on Chelura terebrans* 



the eyes, and are composed of six articulations, whicli, except the 

 second, which is the smallest, do not differ from one another 

 much in size ; these antennae ,thus present no distinct division 

 into peduncle and ramus ; the last four articulations are clothed 

 with long hair, especially on the inferior surface ; the last is flat- 

 tened, and assumes the condition of a fringed oval lamina. The 

 oral appendages consist of a pair of mandibles and two pairs of 

 maxillae, together with an upper and lower lip, the whole being 

 covered in by a pair of large maxillary feet. The mandibles (fig. 3) 

 are very strong, bidentate at the anterior and inner angle, and 

 furnished along their inner edge with long curved spines beset 

 with minute spinulse (figs. 3 & 4) . Between the spines and the 

 base of the mandibles is an oval elevated surface marked wdth 

 transverse ridges which are again crossed at right angles by de- 

 licate striae (figs. 3, 5, 6). This singular eminence must consti- 

 tute a very efficient molar surface, and would seem evidently in 

 connection with the peculiar habits of the animal, though it has 

 its representative in other Crustaceans of the same order. The 

 mandibles support upon their external side a three-jointed seti- 

 gerous palp, and are furnished with powerful adductor and ab- 

 ductor muscles. 



The first pair of maxillse (fig. 7) consist of strong, somewhat 

 pyramidal organs bearing stiff setae at the apex, furnished on the 

 outer side with a two-jointed palp, and carrying at the base an 

 oval fringed lamina analogous to a flagellum. 



The maxillae of the second pair (fig. 8) consist of an elongated 

 lamina supporting a somewhat similar one upon its external edge. 

 This last must be viewed as a flattened single-jointed palp, or 

 else as the terminal joint of a two-jointed stem, the internal la- 

 mina being formed by the basal articulation ; both laminae are 

 terminated by long setae. 



The upper and lower lips (figs. 9 & 10) are fleshy, somewhat 

 conical organs, bounding the buccal cavity anteriorly and pos- 

 teriorly. 



The maxillary feet are united at their origin, and thus consti- 

 tute a sort of great opercular sternal lip which lies over and con- 

 ceals all the other oral organs. Each (fig. 11) consists of a large 

 basal joint supporting a well-developed palp-like stem which is 

 composed of four joints and a terminal incurved claw. The basal 

 joint moreover as well as the first joint of the stem support each, 

 internally, a large plate, thus completing this great opercular lip 

 towards the mesial line of the mouth. 



The thorax consists of seven distinct segments each with a pair 

 of legs. Of these the two anterior pairs are didactyle and di- 

 rected forwards over the mouth. The penultimate and antepen- 

 ultimate joints of the first pair (fig, 12) are clothed with setae 



