([word=service] [□])? □
([word=service] [□=□])? □
([word=service] [□ & □])? □
A - The epiphragm is normally continuous except for a thin grooved slit over the pneumostome which allows reduced respiration to take place . When the muscles contract , the arch flattens and air is drawn in and at the limit of contraction a valve slides across the pneumostome . In such cases the written-off debt is not closed out but classified as CNC . At 14:00 the other snail has gone too . After an hour or so , we encounter a brown snake stretched across the center of the road . The large-scale killing of venomous snakes under the pretense of saving human lives is indefensible , and many of the bites that occur each year befall the misguided people participating in rattlesnake roundups , annual events that occur across the United States to rid natural areas of venomous snakes . This structure is partly extruded from the mouth and licked or scraped across the surface on which the snail is feeding . The deposition of pigment which produces its color pattern is therefore a biochemical record of the individual snail from cradle to grave . The most recent legislative effort - - the Debt Collection Improvement Act of 1996 - - is discussed in detail in appendix IV . A - The direction of movement can be changed by shining a light on just one tentacle . A - The shell is the snails passive mode of defense . A - The muscular strength of snails is surprisingly great .