CIRC E. 



Plate I. 



frenus CIECE, Sclinmacher. 



Tfiifn nunc plano-Jenticnlarh, mnhonihiis compressis, mine 

 ovaf.a, tnrrjida, tniihon'thns corclalis. Cardo tridmtatns, 

 dentihtis iiifequolibiis, diverf/cntibus, antico lateraliler 

 elongato. Impressio pnUii simplex, hand shniata. 



Sliell sometimes flatly lens-shaped with the umboes com- 

 pressed, sometimes ovate and turgid witli the um- 

 boes cordate. Hinge three-toothed, teeth unequal, 

 diverging, the anterior laterally elongated. Impres- 

 sio7i of the mantle simple, not sinuated. 



In this group of about fifty species, all of which, so far 

 as the habitats are at present known, are, with a single 

 exception (C. numnmUnu), inhabitants of the Eastern He- 

 misphere, we have two apparently very dissiuiiliar forms. 

 In tiie first of these, of whieii the Linneean Venm scripta 

 {Ci/therea scripta. Laniarck) is the type, the sliell is sin- 

 gularly fiat, compressly pinched at the umboes ; in the 

 second, of which the Linnrean J'cnus castrcnsis {Ci/lherea 

 castrensis, Tjainarck) is the type, the shell is ovately turgid, 

 with tiie uinboes cordate. And, intermediate between 

 these forms, a very characteristic link is presented in the 

 Liimsean Venus pectiiiatn {Cyllierea pectinata, Lamarck), 

 with the sculpture peculiarly divaricate, whicli divarication 

 is present in C. intermedia, a member of the C. castrensis 

 group. All are distinguished generically by the absence of 

 any posterior sinus in the pallial impression. C. castrensis 

 and its congeners have been separated as a subgenus by 

 Jlorch, under the title Lioconcha. 



With the exception of the single Central American spe- 

 cies already mentioned, and the two small European spe- 

 cies C. rudis autl minima, the Circe iidiabit exclusively 

 the Indian Ocean (including the Piiilippine Islands), Aus- 

 tralia, and the Red Sea, and C. giljl)a, pectinala, and diva- 

 ricatu, belonging to the intermediate group, iidiabit, curi- 

 ously enough, all of these three localities in common. It 

 should be added, howevei-, that it is only of about one- 

 half of the Circe that the habitats are as vet known. 



Species 1. (Fig. a, b, c, Mus. Cuming.) 



Circe scripta. Circ. testa subquadrato-lentiformi, com- 

 pressd, postici' anijidate iruncatn, fulvescente-albd, cas- 

 taneo-fusco lineari-undatd , pterumyue biradiatim via- 

 culald, conceutrice crebriliratd, nmbonibus plauo-com- 

 pressis. 



The written Circe. Shell somewhat squarely lens- 



shaped, compressed, posteriorly angularly truncated, 

 fulvous-white, linearly waved with chestnut-brown, 

 generally biradiately blotched, concentrically eloselv 

 ridged, umboes flatly compressed. 



Veuns scripta, Linnrens, Syst. Nat. p. 113.5. 

 Vytlierea scripta and undatinn, Lamarck. 



Hub. Eastern Seas. 



The shell represented at Fig. 1 c is, I believe, the va- 

 riety named Ci/tkerea undatina by Lamarck. It is some- 

 what conspicuously removed from the normal type of the 

 species, Fig. 1 b, but tliis species is one of the most vari- 

 able of the genus. 



Species 2. (Fig. a, b, Mus. Cuming.) 



Circe pijcatina. Circ. testa, oblique lenticulari, crus- 

 siuscnld, postici; rotundato-truncatd, fulvescente-albd, 

 iiigricante-cnstaneo reticulato-uudatd, coucentrice va- 

 lide corr uijatu-plicatd . 



The pleated Circe. Shell obliquley lens-shaped, 

 rather thick, posteriorly rotundately trancated, ful- 

 vous-white, reticulately waved with dark chestnut, 

 coiioentrically strongly wrinkle-pleated. 



Cijllierea pticatina, Lamarck, Aiiim. sans vert. vol. vi. p. 336. 



Ilab. New Holland. 



This is a stouter and more convex species than C. 

 scripta, of a peculiar oblique, instead of square growth, 

 very strongly concentrically pleated. 



Species 3. (Fig. a, b, Mus. Cuming.) 



Circe rivulauis. Circ. testa, subquadrato-lentiformi, 

 depressisshnd, fuleescente-albd, spadiceo-rnfu radiatim 

 nebulatd, circa umbones taciffatd, delude concentrice 

 rude liratd, ad latera exiliter diagonaliter rugafd. 



The rilled Cihce. Shell somewhat squarely lens- 

 shaped, very depressed, fulvous-white, radiatelv 

 clondcfl with fawn-red, smooth around the umboes, 

 then concentrically rudely ridged, at the sides faintly 

 diagonally wrinkled. 



Venns rivularis, Born, Test. Mus. Vindob. p. 72. pi. .5 

 f. 7. 



Cijtherea rivularis, Menke. 

 Circe rivularis, Sovverby. 



Ilab. New Holland. 



A pale, very depressed species, radiately clouded with 

 fawn-red. 



February, lSG-1'. 



