On the Lysianassa magellamca etc. 



13 



proach to or recede from one another like jaws, to which they have 

 some resemblance. The external build is composed partly of thinner chi- 

 tinous laminae and partly of more solid chitinous ribs which form the solid 

 support of the former. The upper lip is somewhat distended and convex 

 and has near its apex a sharp indentation, from which that apex bends 

 itself inwards almost like a bird of prey's beak. The middle portion of 

 the inner or palate side has two bristley-ribs united both in front and back 

 and diverging in the middle, separated at the back by a notch from the 

 curved apex of the beak. The side-pieces of the under lip are more solid 

 but thin and flattened though uneven. (Fig. 5. b, b from the exterior, fig. 5 

 from the interior). At the projecting, free, indented end [a) they are yellow- 

 ish, and their inner edge from the point to the base is armed with a thick 

 row of short bristles, so that they are evidently employed in dividing the 

 animal's food and conveying it to the swallow. The mandibular are inserted 

 between the upper and lower lips and are thus for the greatest part of their 

 length separated from the maxillae. 



The mandibulae (Fig. 3. d. d and figg. G & 7, the left) are about 

 5 y 2 millim. long and peculiarly strongly formed. The masticating extre- 

 mity (Fig. G a from the interior) which is bent inwards as Ave see it in 

 fig. 7. a, has a sharp, cutting and even or toothless edge. This edge has 

 but a slight groove on each side, from which proceeds on the inside a curved 

 and somewhat raised line. At the middle of that line is a very small and 

 simple accessory process ("processus accessorius", Bruzelius ') ) , and from 

 that a raised edge thickly armed with at first somewhat coarser and longer 

 but afterwards shorter and finer bristles, which afterwards passes over to 

 the "tuberculum molare" Bruzelius, (b) of which it forms the outer edge, 

 and when there is thickly set with short bristles. Between these outer 

 edges the tuberculum molare is hollowed out. On the fore side of the man- 

 dibula about halfway between the masticating end or edge and the insertion 

 of the palp is a strong almost ball-like notch (Fig. 6. c). The palp (d) 

 is large, and consists as usual of 3 joints of which the middle one is the 

 largest and longest, and is broadest in the middle, and it, as well as the 

 3 1 joint, carry a number of sharp bristles. The palp reaches to about the 

 end of the last joint but one of the lover antennae's shaft. Fig. 7 shows 

 the left mandibula seen from the outer side. As the masticating extremity 



') Bruzelius (Skandrs Ampliipoda Grammaridea) denies the existence of such a 

 process in the genus Anonyx; we have however found it in the most species. 



