136 MOLLUSCA FROM THE CRAG. 



3. Margarita teochoidea S. Wood. Tab. XV, fig. 2. 



Margarita trochoidea. S. Wood. Catalogue 1842. 



M. Testa-orb iculato-troc/iided, depressd, tenui,frac/ili; apice obtusiusculo, anfractibus 

 q>t alitor, convexis, superne depressis apud suturas, ad basim obtuse angulatis, subtus rotun- 

 datis ; transversim tenuissime striatis ; aperturd suborbiculari ; umbilico rnagno prof undo. 



Shell depressedly conical, trochiforin, thin, and fragile ; volutions four, convex 

 above, slightly flattened near the suture, convex or rounded beneath, with an 

 obtuse angle at the outer edge ; covered with fine transverse or spiral stria? ; aper- 

 ture subcircular, impressed by the body whorl with a sharp expanded and curved 

 outer lip ; umbilicus large and deep. 



Axis, \ of an inch ; diameter f . 



Locality. Cor. Crag, Sutton. 



Fragments and small specimens of this species are abundant. The diameter 

 of the base of the specimens figured does not exceed three eighths of an inch, 

 although fragments indicate at least half an inch. The volutions are convex both 

 above and beneath the subcarinated edge, and the umbilicus is visible to the spire, 

 characters that distinguish this species from any other with which I am acquainted. 



Adeorbis,* 8. Wood. 1842. 



Helix (spec.) Mont. 

 Trochus (spec.) Brown, Nyst. 

 Cingula (spec.) Flem. 

 Natica (spec.) Phil. 

 Valvata (spec.) Phil. 

 Delphinula (spec.) Bast. 

 Margarita (spec.) S. Wood. 



Gen. Char. Shell generally small, suborbicular, depressed, with a few nearly 

 discoidal and rapidly increasing volutions, umbilicus large and deep ; peritreme 

 entire, and nearly continuous, slightly interrupted by the previous volution, deeply 

 sinuated on the inner side, and having a minute or incipient sinus at the upper part 

 of the aperture, near the junction of the body whorl. 



As there was not any genus established at the time I compiled my Catalogue in 

 which I could place some small shells from the Crag, possessing the above characters, 

 the above name was proposed for their reception. Conceiving that an animal with 



* Etym. Adeo, to approach, orbis, a circle. 



