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The mollusks which come under the common appellation of Slugs have no 

 shell beyond a small ear-shaped shield, commencing in its development from 

 an obtuse subspiral nucleus) serving for the protection of the pulmonary 

 cavity of the animal, which is situated sometimes, as in Limax, near the 

 head, sometimes, as in Parmacella, in the middle, and sometimes, as in 

 Testacetta, near the tail ; and it is only in th,e last instance that the shell 

 is external and exposed to view. In addition to these, there are one or 

 two genera having either no shell at all, or the merest rudimentary frag- 

 ment in the shape of a few calcareous grains. The Limacinea, so far as 

 they have been observed, inhabit chiefly the temperate regions, and are 

 more carnivorous than vegetable feeders. Divested of any shelly encum- 

 brance, or having it only moderately developed on the tail, they are able 

 to burrow into the ground to the depth of nearly two feet ; sometimes, 

 however, they suspend themselves from trees by means of a gelatinous 

 thread.* The shell-secreting genera are — 



Testacella. Limax. Parmacella. 



Genus 1. TESTACELLA 



Animal ; elongated, semicylindrical ; disc covering and combined 

 with the entire upper surface of the body, which bears an ex- 

 ternal shell at the hinder extremity of the back ; head toith four 

 tentacles, the upper ones bearing the eyes. CForbes.J 



Shell ; ear-shaped, rather compressed, covered with a brownish 

 epidermis ; spire very small, obtuse. 



The Testacella is a small carnivorous slug, feeding chiefly on worms, and 

 having the habit during the winter of burrowing in the ground to the 

 depth of one to two feet. As if for providing, under these circumstances, 

 a place of security for the more delicate organs, the pulmonary cavity of 

 the animal is situated in the rear under the protection of a rather strong, 

 compressly auriform shell. The whole of the shell is exposed, and its 

 spiral nucleus is a little beaked and reaches nearly to the posterior edge 



* "All the species," says Dr. Binney, of the United States, "that have come under my 

 notice possess the power of suspending themselves in the air by a gelatinous thread. This they 

 effect by accumulating a quantity of tenacious mucus at the posterior extremity of the foot, 

 which they attach to the object from which they are to commence their descent ; then, loosing 

 their own hold, they hang suspended by this point. Continuing the secretion, their own weight 

 attenuates the mucous attachment, and draws it out into a thread. As this dries and hardens a 

 fresh supply is afforded, the thread is lengthened, and the animal lets itself down any desirable 

 distance. At this time also the margin of the foot pours out mucous freely, and during the 

 whole operation the locomotive disc is in active undulatory motion." Terr. Moll. U. S. v. 2, p. 4. 



