Need help to identify Costa rica Pacific shell....beginner issue

[Argonauta]

I need to identify some shell I found on the waters of the South pacific coast of Costa Rica.
I am a beginner, and I need to know which book or catalog could help me to identify shells of my area.
Thanks a lot for the help.
the shell I need to identify are the following ones :

<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028392">http://www.badongo.com/pic/13028392</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028393">http://www.badongo.com/pic/13028393</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028394">http://www.badongo.com/pic/13028394</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028395">http://www.badongo.com/pic/13028395</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028402">http://www.badongo.com/pic/13028402</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028411">http://www.badongo.com/pic/13028411</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028412">http://www.badongo.com/pic/13028412</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028435">http://www.badongo.com/pic/13028435</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028440">http://www.badongo.com/pic/13028440</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028442">http://www.badongo.com/pic/13028442</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028443">http://www.badongo.com/pic/13028443</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028447">http://www.badongo.com/pic/13028447</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028448">http://www.badongo.com/pic/13028448</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028449">http://www.badongo.com/pic/13028449</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028450">http://www.badongo.com/pic/13028450</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028454">http://www.badongo.com/pic/13028454</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028455">http://www.badongo.com/pic/13028455</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028460">http://www.badongo.com/pic/13028460</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028464">http://www.badongo.com/pic/13028464</a><!-- m -->


thanks a lot for the help

[paul monfils]

Hello! Welcome aboard!  I'll see what I can do with these, but for the future, two recommendations - first, take your pictures straight-on, not at various angles.  This makes it more difficult to determine the actual shape of the shell.  Lay a bivalve flat on the table, and shoot it from directly above, looking straight down.  With gastropods, position the shell on a lump of modeling clay so that you get a straight-on shot of the dorsal view and the ventral view, again shooting straight down.  Secondly, mention the size of each specimen you post.  Sometimes two species are similar, but one of them doesn't exceed an inch in length and the other may be much larger.

The book you need is Sea Shells of Tropical West America by Myra Keen.  Unfortunately it is out of print, and copies when available are pretty expensive.

<!-- m --><a class="postlink" href="http://www.alibris.com/booksearch?qisbn=9780804707367&qsort=p&cm_mmc=shopcompare-_-pricegrabber-_-books-_-used">http://www.alibris.com/booksearch?qisbn ... oks-_-used</a><!-- m -->

There are copies of her earlier book (same title, I believe) on Amazon.com pretty cheap.  The book is more than 50 years old and smaller than the one listed above, but you still might find it useful.

<!-- m --><a class="postlink" href="http://www.amazon.com/Sea-shells-tropical-west-America/dp/B0006AVH92/ref=sr_1_9?ie=UTF8&qid=1306193743&sr=8-9">http://www.amazon.com/Sea-shells-tropic ... 743&sr=8-9</a><!-- m -->

OK, on to the shells:

392/393 - Cymatium (Septa) vestitum
394/395 - Astraea buschii
402 - Tellina sp., best guess Tellina eburnea
411/412 - Cardita affinis
435 - May be Pitar roseus (the angle makes it hard to tell).  Could also be Pitar lupanaria, with the spines worn off.
440/442 - Too worn to be certain, best guess Crepipatella dorsata
443 - Donax sp., best guess Donax navicula
447/448 - Donax sp., best guess Donax peruvianus
449/445 - This a land snail, probably a species of Lampadion
454/455 - Trivia radians
460 - Olivella sp., best guess Olivella volutella (again, poor angle, and ventral view would help)
464 - Terebra robusta

.

[Argonauta]

Hi Paul, thanks a lot, really a lot, about the tips and the identification.
using your identification I started looking for these shells here and there, and I found some shell that look a lot to the Trivia radians, but are identified as Trivia solandri.
look at : <!-- m --><a class="postlink" href="http://cgi.ebay.com/19-20-mm-3-Pcs-Trivia-Solandri-Sea-Shell-SeaShell-/230625579836?pt=LH_DefaultDomain_0&hash=item35b25b133c">http://cgi.ebay.com/19-20-mm-3-Pcs-Triv ... 35b25b133c</a><!-- m -->
they look very , very similar to the specimen I have....what is the difference between these two species?
thanks again for everything.

bests

[paul monfils]

Yes, Trivia radians and Trivia solandri are very similar, and I have seen a few specimens where I couldn't decide for certain.  Unfortunately there isn't one clear cut characteristic you can use to separate them in all cases.  But in general, T. radians is broader for its length (smaller length:width ratio), more oval in outline (T. solandri tapers more anteriorly), more dorso-ventrally depressed (flattened), lighter in color, and often has a dark blotch on the top of the dorsum (as yours does).  Keen states that T. solandri has "a few less transverse ribs" than T. radians, but doesn't provide any actual counts.  In my opinion, the swollen nodes along the mantle line on the dorsum are usually more pronounced in T. solandri.  T. radians grows larger (16-22 mm usual size range, compared with 13-16 mm for T. solandri), and T. solandri ranges farther north, into California, U.S.A.  Both species are found in your locality.

You can see several specimens of each here: <!-- m --><a class="postlink" href="http://www.conchology.be/?t=65&family=TRIVIIDAE">http://www.conchology.be/?t=65&family=TRIVIIDAE</a><!-- m --> (though I believe the last specimen shown as T. radians is actually a large T. solandri).

[Argonauta]

Hi Paul, Thanks again for to share your knowledge.
I would try to have some more help in the identification of some other shells I found in my area.here the links to the pictures, and excuse me if they are similar to the first ones , in term of wrong angle, but , I swear, the next ones will fit your counsels....

<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028459">http://www.badongo.com/pic/13028459</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028458">http://www.badongo.com/pic/13028458</a><!-- m -->

<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028457">http://www.badongo.com/pic/13028457</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028456">http://www.badongo.com/pic/13028456</a><!-- m -->

<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028452">http://www.badongo.com/pic/13028452</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028451">http://www.badongo.com/pic/13028451</a><!-- m -->

<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028400">http://www.badongo.com/pic/13028400</a><!-- m -->
<!-- m --><a class="postlink" href="http://www.badongo.com/pic/13028398">http://www.badongo.com/pic/13028398</a><!-- m -->

...and by the way, about Trivias, are more common the Solandri Or the Radians ?

Thanks again for your help

Bests

[paul monfils]

Hi,

398/400 is Chione subrugosa

451/452 are either Cypraea arabicula and/or Cypraea robertsi, difficult to separate when they are this beachworn.  I could go out on a limb and say that the apparently more narrow shell with the darker ground color, on the left is more likely C. arabicula, and the broader shell with the lighter ground color is more probably C. robertsi.  You will probably find better specimens, since both of these are common in your area.

456/457 is a Cerithium, best guess Cerithium gallapaginis, not sure

458/459 is Planaxis planicostata

Keens lists both the Trivias as "moderately common", but I believe T. solandri is more common than T. radians.

If you have additional shells to post, please start a new thread, so this one doesn't become too long.

Paul M.

[Argonauta]

thanks a lot, again, and, I will open a new post, as I will take some good shoot of new shells I will find.
Have a good time

Bests