OCR Text |
Show 1893.] AOARUS FOUND IN CORNWALL. . 267 the organ, when at rest, is supported in a notch formed by two short rods attached to triangular blade-like sclerites on edge. The legs are short, the posterior pairs not reaching the hind margin of the body; the two front pairs are almost blade-like, 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 curved. 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 that 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 moArement as the creature moves or feels about. It would seem to have become a tactile organ or one for collecting food. There 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. 6). Habitat. I found numerous specimens in a patch of green alga (Cladophora fracta) growing where the fresh water of a small stream trickled over the face of the granite cliffs within reach of the spray of the sea, near the Land's End, Cornwall. I have not found it elsewhere. EXPLANATION OF PLATE XVIII. All the figures represent Lentungula algivorans. Pig. 1. Adult 5 seen from above, X150. 2. Adult 5 seen from below, X 150. 3. Adult j seen from below, X 150. 4. Second left leg (drawn from the c$ , but similar in both sexes), side view, x320. 5. Tarsus of 1st left leg, X 320. 6. Claw of 4th leg (drawn from <$, but sexes similar), X 320. 7. Left mandible of $ seen from the inner side, X 320. 8. Maxillary lip, palpi, and (?) labium seen from below, X 320. 9. Penis and penial skeleton and sclerites seen from below, X 320. 10. Penis seen from the side, X320. |