696 Some Account of the 



dorsal ridge or keel, which is then free from all corrugation. 

 The hinder portion of the body is considerably compressed, 

 and in the young ones so much so, that it is the most striking 

 of their features. A specimen, not of the very largest size, I 

 consider, which I measured a month or so ago, when it was 

 travelling, and at its greatest extension, was nearly three inches 

 long, and of this length the shield or mantle measured three 

 quarters of an inch. The dorsal ridge or keel was straight 

 and unwaved ; but when the animal, from being interrupted, 

 contracts itself, this keel or ridge is folded by the contraction 

 into transverse wrinkles. The lateral orifice in the travelling 

 slug was riot more than large enough to admit the head of an 

 ordinary pin, into and out of which parasitic mites were 

 nimbly passing. The upper tentacula, or horns, were about 

 four tenths of an inch long, and their tips not abruptly thick- 

 ened or set on. 



To acquire food is, of course, the principal motive for tra- 

 velling in this species, as in every animal; but I regret my 

 inability to state on what substances it mainly subsists. The 

 imperfect attention my want of time has allowed me to 

 give to it has not discovered to me that it preys much on 

 the growing foliage of plants, although it seems not averse to 

 decaying vegetation. I have found it on partly skeletonised 

 leaves, that had been some time on the ground, of the apple 

 tree, and I thought it was eating away the fleshy part : it will 

 eat off the cuticle of the stems of the potato, when these are 

 beginning to decay in autumn. I think rather it is a foul 

 feeder, eating coarse fare, and not refusing even carrion ; for I 

 have known it to feed on potato tubers and thrown away rotten 

 ripe gooseberries, and I have found individuals devouring the 

 dead remains of each other, every part of which they seem to eat, 

 except the skin of the back, and I am not quite certain that 

 they always wait for the dead remains of each other. Gardeners 

 accuse them of greedily devouring growing mushrooms raised, 

 as about London they are abundantly, by artificial cultivation. 

 Sometimes a young one will eat its way into a potato, and, 

 having entered, eat away all the interior, and become there 

 much too large to make exit by the hole at which it entered. 



Parasitic mites are plentiful on the full-sized individuals of 

 Z/imax Sowerby/, and I think more plentiful in autumn than 

 in summer, and even in wet weather in autumn ; whether of 

 the species Philodromus Z/imacum Jenyns^ vol. iv. p. 538., or of 

 a distinct species, I have not the means to determine. I had 

 years ago observed mites running about the bodies of slugs^ 

 but was totally ignorant of that information on their person 



