LIMACID^. 5 



periodically to the surface for the purpose of respiration. 

 They have distinct heads, and are furnished with ten- 

 tacul^ and eyes. They move by the contraction of the 

 disks of their body. 



The shells, when present, are mostly spiral or dis- 

 coid, sometimes patelliform. They are mostly external. 

 In the few instances in which they are internal, thev 

 are imbedded in the mantle, and shaped like the finger 

 nail. They are hermaphrodite, and produce their 

 young by eggs, in which the embryos are observed par- 

 tially clothed with cilia, the movements of which are 

 obvious. 



In this section we have six tribes. 



Tribe I. — Limacid^. 



Animal — The well-known land slug. Body semi-cylindrical, soft 

 and fleshy, secreting abundant mucus through the pores 

 of the skin; the breathing cavity covered by a cloak or 

 disk, in the right margin of which the respiratory orifice, 

 and the vent are observable ; the head retractile with 

 four retractile tentacles, the upper two provided with 

 eyes ; mouth furnished with teeth, with single and long 

 projecting tops. 



Shell — Either wanting or embedded in the cloak or disk which 

 covers the front part of the body. They feed either at 

 twilight or during the night. It includes three genera 

 — Alien, Geomalacus and Limax. 



Tribe II. — Testacellid^. 



Ani/nal — With elongated body, semi-cylindrical, tapering in 

 front; disk covering and combined with the upper surface 

 of the body, bearing an external shell at the hinder part 

 of the back ; head with four tentacidce, the upper two 

 bearing the eyes, breathing orifice under the right side of 

 the shell, the vent near to it ; reproductive orifice behind 

 the upper tentacle on the right side. 



Shell — External, earshaped, compressed, with a very short 

 spire ; mouth very large with a thin outer Up slightly 

 notched at the hinder part. It contains one genus — 

 Testacellus. 



