- In Palmer notation, each quadrant of the mouth is assigned a specific symbol, and the teeth within each quadrant are numbered from the midline (central incisor) moving posteriorly to the third molar.
- The numbering for permanent teeth starts at 1 for the central incisor and continues to 8 for the third molar.

- The symbol '└' signifies the lower left quadrant of the mouth.
- The number '4' refers to the first premolar in that quadrant.
- Therefore, the symbol '└4' specifically denotes the lower left first premolar.

To summarize:
- Palmer notation uses quadrant symbols:
- '┌' for upper left
- '┐' for upper right
- '└' for lower left
- '┘' for lower right
- Tooth numbers range from 1 to 8, starting from the midline.
- '└4' = Lower left first premolar.

Hence, the correct answer is Option 1: Lower left first premolar.

Reference: Orban's Oral Histology, Volume 1, Chapter 3, Page 45