Commonly called the Sundial shell, Architectonica is small. The specimen shown in this photo is probably less than an inch across.
![Sundial Seashell 1 by Harold Davis Sundial Seashell 1 by Harold Davis](https://www.digitalfieldguide.com/images/sundial-seashell-1.jpg)
Turn the shell over, and there’s a tiny spiral formation going down into the core of the shell. This spiral looks like a staircase—but don’t forget how small it is. The version shown here is greatly magnified, probably twenty or thirty times life size.
![Architectonica Spiral 1 by Harold Davis Architectonica Spiral 1 by Harold Davis](https://www.digitalfieldguide.com/images/architectonica-spiral-1.jpg)
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