Fissurella and Drymaeus (Mexico)?

[wolf]

Hi,
yesterday evening I was very happy to find this excellent "high end" forum and I will be glad to join it. I´m from Germany, so please apologize my terrible English. Concerning gastropods, I´m an absolute beginner.
I´m just musing on two shells from Mexico, perhaps someone can help me along.
The first species might be <i>Fissurella barbadensis</i> (GMELIN, 1791). Both specimen (with intensive greenish colour on the inside) were found at Xcacel (east side of peninsula Yucatán, State of Quintana Roo, 23.07.1999), length of shell 18 and 21 mm. I´m not sure about the curious "furred" structure of the surface (whether it might be some strange periostracum or produced by some other organism). The other shell of the same species is free of it.  
<img src="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbPUFo1.jpg" alt="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbPUFo1.jpg" style="border:0" /><img src="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbPO1Fo1.jpg" alt="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbPO1Fo1.jpg" style="border:0" />
<img src="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbSO1Fo1.jpg" alt="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbSO1Fo1.jpg" style="border:0" /><img src="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbSSFo3.jpg" alt="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/FissBarbSSFo3.jpg" style="border:0" />
The other species might be <i>Drymaeus serperastrum</i> (SAY, 1829), hight 34,6 mm (Mexico, State of Yucatán, Valladolid, Cenote Zaki, 26.07.1999). Could it be right?
<img src="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/DrymaeusSerperastrumFo1.jpg" alt="http://i803.photobucket.com/albums/yy320/wolfsnail/Mexiko1/DrymaeusSerperastrumFo1.jpg" style="border:0" />
Thanks a lot for your help <img src="images/smiley/smile.gif" alt="" border="0" />, kind regards: wolf

[paul monfils]

Hello Wolf,

Welcome to the list.  I'm sorry it has taken so long to respond to your post.  Your limpet is certainly Fissurella barbadensis.  The green interior (actually alternating green and light bands) is a key characteristic of this species.  The fuzzy stuff covering the exterior is calcareous algae, which frequently grow on these shells. The Drymaeus is more difficult, mainly because I don't know land snails as well as marine shells.  The species you mentioned, D. serperastrum, which I was totally unfamiliar with, doesn't seem to have many references available. I can't find it in any book in my library, and even online information is sparse.  However, from the couple of images I was able to locate, I think your ID is probably correct.

[wolfi]

Hi Paul,
thanks a lot for your help . Now I´m a little bit more sure about my guess. I found Drymaeus serperastrum in Pilsbry (Manual of Conchology). The description seems to fit my specimen more or less, but I have no shells of this species here to compare with........ .
Thanks again for your help,
kind regards: wolf