C Y C L S T R E M A. 



Genus CYCLOSTHKN(A, Manjalt. 



TeMa orbiculata, depri'ssa, /air nmliilintUi : spini parva, 

 anfraclibus spiraliter et (■(niceiitrirr, plus 7Hiiiiisve 

 Urala vcl sulcata. Apirtura inte/jra, hand nacrca, 

 margiiie acii/o. 



Shell orbicular, depressed, broadly umbilicated ; spire 

 small, whorls spirally and concentrically ridgod or 

 sulcaU'd. Aperture entire, not pearly, margin 

 acute. 



Some of the smaller species of DelpJiinula resemble 

 these little shells, which, with Adeorbis and the sub- 

 genera of both make a natural group. The difference 

 between the two genera is that Cydostrema has more 

 external sculpture and a wide umbilicus, which in 

 Adeorbis is wanting. Of the twenty-three species 

 included in this genus and its subgenera Daionia, 

 Tubiola, Microlheca, and Mot-chia, a dozen were found 

 by Mr. Arthur Adams on the coasts of Japan, half-a- 

 dozen more wore collected by the late Mr. Cuming 

 amongst the Philippines, leaving five or six for such 

 widely distant localities as Britain and Australia, 

 China and California, &c. 



Species 1. (Fig. a, b, Mus. Brit.) 



CVCLOSTREMA CINGITLIFKRA. CyC. tcstt't Orbicuhui, 



depressa, a7ifiaclibus rapide crescentibus, n/limo 

 ca7-inis sex acutissimis, prominentibus cincto ; iim- 

 hilico lata, piano ; aperturd rotmidd, margine 

 externa superne laqumto. 



The belted Cyclostrema. Shell orbicular, depressed, 

 whorls quickly increasing, the last encircled with 

 six prominent, very sharp ribs ; umbilicus wide, 

 flat ; aperture rounded, outer margin fluted. 



A. Adams. Proc. Zool. Soc, 1850. 



Hub. Isl. of Negroes, Philippines. Japan. 



Species 2. (Mus. Brit.) 



Cyclostrema excavata. Ci/c. testa romplanatd, minu- 

 ti,-:siiiie spiraliter striatd ; aiij'nicli/ntx rapide cres- 

 centibus, nltimoanj'ractu infra •iiniulatii. idinplanato; 

 umbiliro lata ; aperturd obliqiia, vian/iiic tenui. 



The excavated Cyclostrema. Shell llattened, very 

 minutely spirally striated ; whorls rapidly increas- 

 ing, last whorl angular, flattened beneath ; umbili- 

 cus broad ; aperture oblique, margin thin. 



Carpenter. Proc. Zool. Soc, 1850. 



Ilab. China Seas. 



Species 3. (Mus. Brit.) 



Ctclostrema sulcata. Cijc. trsiil ,.rhiri,/ari, depressd, 

 regulariter spiraliter sulcala . >pir,'i rahir depressd ; 

 ultimo anfractu lata; umbiliro talissiiiio, sulcata; 

 aperturd fere rotundd. 



The sulcated Cyclostr.ema. SIrII orbicular, de- 

 pressed, regularly spirally sulcated ; spire much 

 depressed ; last whorl broad ; umbilicus very 

 wide, grooved ; aperture nearly round. 



A. Ai.AMs. Proc. Zool. Soc, 1850. 



Ilab. Philippines. Japan. 



Species 4. (Fig. a, b, Mus. Ci 



CVCL0STI;EMA VeRRAUXII. 



Cyc. testa orbiculatd, de- 

 j)ressd, spird parvd, anfnirtibus subquadratis, 

 rapide crescentibus ,- vltiiiin aiifrnclu tricarinato, 

 carind viediand pnanin, nli. a, I ,i/i, rlurant in lobam 

 lingntformemprodtui,^ ,■ uiiihi/ir(, mnliarri, planato ; 

 aperturd magna, labia cvlrnai inj'rd ainjiilato, medio 

 lingulatim p?-oducto. 

 Verkaux's Cyclostrema. Shell orbicular, de- 

 pressed, spire small, whorls rather square, rapidly 



June, 187-1. 



