Looks like a young Aegista mackensii. Why have extensions only on the periphery?

Looks like a young Aegista mackensii. Why have extensions only on the periphery?
Grab edinburgh woolen mill the HTML/BBCode
<iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="350" width="500" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe> <iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="70" width="100" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe> <a href="https://www.flickr.com/photos/artour_a/3037008619/" title="Hairy snail (Aegista mackensii), Taiwan by Arthur Anker, on Flickr"><img edinburgh woolen mill src="https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_t.jpg" width="100" height="70" alt="Hairy snail (Aegista mackensii), Taiwan"></a> [url=https://www.flickr.com/photos/artour_a/3037008619/][img]https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_t.jpg[/img][/url] [url=https://www.flickr.com/photos/artour_a/3037008619/]Hairy snail (Aegista mackensii), Taiwan[/url] by [url=https://www.flickr.com/people/artour_a/]Arthur Anker[/url], on Flickr <iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="75" width="75" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen edinburgh woolen mill oallowfullscreen msallowfullscreen></iframe> <a href="https://www.flickr.com/photos/artour_a/3037008619/" title="Hairy snail (Aegista edinburgh woolen mill mackensii), Taiwan by Arthur Anker, on Flickr"><img src="https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_s.jpg" width="75" height="75" alt="Hairy snail (Aegista mackensii), Taiwan"></a> [url=https://www.flickr.com/photos/artour_a/3037008619/][img]https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_s.jpg[/img][/url] [url=https://www.flickr.com/photos/artour_a/3037008619/]Hairy snail (Aegista mackensii), Taiwan[/url] by [url=https://www.flickr.com/people/artour_a/]Arthur Anker[/url], on Flickr edinburgh woolen mill <iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="150" width="150" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe> <a href="https://www.flickr.com/photos/artour_a/3037008619/" title="Hairy snail (Aegista mackensii), Taiwan by Arthur Anker, on Flickr"><img src="https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_q.jpg" width="150" height="150" alt="Hairy snail (Aegista mackensii), Taiwan"></a> [url=https://www.flickr.com/photos/artour_a/3037008619/][img]https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_q.jpg[/img][/url] [url=https://www.flickr.com/photos/artour_a/3037008619/]Hairy snail (Aegista mackensii), Taiwan[/url] by [url=https://www.flickr.com/people/artour_a/]Arthur Anker[/url], edinburgh woolen mill on Flickr <iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="168" width="240" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe> <a href="https://www.flickr.com/photos/artour_a/3037008619/" title="Hairy snail (Aegista mackensii), Taiwan by Arthur Anker, on Flickr"><img src="https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_m.jpg" width="240" height="168" alt="Hairy snail (Aegista mackensii), Taiwan"></a> [url=https://www.flickr.com/photos/artour_a/3037008619/][img]https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b_m.jpg[/img][/url] edinburgh woolen mill [url=https://www.flickr.com/photos/artour_a/3037008619/]Hairy snail (Aegista mackensii), Taiwan[/url] by [url=https://www.flickr.com/people/artour_a/]Arthur Anker[/url], on Flickr edinburgh woolen mill [url=https://www.flickr.com/photos/artour_a/3037008619/]Hairy snail (Aegista mackensii), Taiwan[/url] by [url=https://www.flickr.com/people/artour_a/]Arthur edinburgh woolen mill Anker[/url], on Flickr <iframe src="https://www.flickr.com/photos/artour_a/3037008619/player/a0cef5f94b" height="350" width="500" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen edinburgh woolen mill msallowfullscreen></iframe> edinburgh woolen mill <a href="https://www.flickr.com/photos/artour_a/3037008619/" title="Hairy snail (Aegista mackensii), Taiwan by Arthur Anker, on Flickr"><img src="https://farm4.staticflickr.com/3162/3037008619_a0cef5f94b.jpg" width="500" height="350" alt="Hairy snail (Ae