1893.] ACARUS FOIiyD Ilf CORNWALL, 267 



the organ, when at rest, is supported in a notch formed by two 

 short rods attached to triauguhir blade-Hke sclerites on edge. 



The legs are short, the posterior pairs not reaching the hind 

 margin of the body ; the two front pairs are ahnost blade-hke, so 

 that when seen on edge they appear almost linear, but they are 

 rarely seen in this position ; they are usually turned at an angle 

 so that the side is partly seen, and thus they look very broad; they 

 are much cur^-ed. The only remarkable feature is the tarsus (fig. 5), 

 which in these two pairs is strongly curved and bluntly pointed, 

 so that the whole joint forms a great claw, and it is by this tliab 

 the creature climbs. It, however, is not the true claw, that 

 exists in addition ; from the side, not the end, of the claw-like 

 tarsus springs a fine transparent, flexible tube which projects 

 considerably beyond the tarsus ; this tube ends distally in a small 

 hollow ball, from which the very minute, but perfectly distinct, 

 real claw arises. The tube can be flexed in almost any direction 

 at the will of the creature ; the ball also is capable of separate 

 articulate motion upon the tube, but the claw does not seem 

 capable of movement separately from the ball. I have not seen 

 this apparatus used in clinging, but it is in continual special 

 movement as the creature moves or feels about. It would seem 

 to have become a tactile organ or one for collecting food. I'here 

 is a short curved spine on the underside of the tarsus, a strong 

 spike on the underside of the tibia, and some hairs, the 

 arrangement of which may be seen from the drawings. The two 

 posterior pairs of legs are quite different from the anterior : they 

 are ordinary rounded legs, rather small, without any special 

 feature ; the tarsi are of the ordinary nature, and are terminated 

 by large, single, curved claws (fig. 0). 



Habitat. I found numerous specimens in a patch of green alga 

 (ChuhjiJiora fracta) gro^nng where the fresh \Aater of a small 

 stream trickled over the face of the granite cliffs Mithin reach of 

 the spray of the sea, near the Laud's End, Cornwall. I have not 

 found it elsewhere. 



EXPLAlfATION OF PLATE XVIII. 

 All the figures represent Lentungula algivorans. 



Fig. 1. Adult $ seen from above, XloO. 



2. Adult 2 seen from below, X 150. 



3. Adult (S st^en I'roin below, X 150. 



4. Second left leg (drawn from the (S , but similar in both sexes), side 



view, x320. 



5. Tarsus of 1st left leg, X320. 



6. Claw of 4th leg (drawn from (^ , but sexes similar), x320. 



7. Left mandible of '? seen from tiic inner side, x320. 



8. Maxillary lij), jialj)!, and (?j labium seen from below, X3'20. 



9. Penis and peuial skeleton and sclerites seen from below, X3-J0. 

 10. Penis seen from the side, X 320. 



