69 



Genus 12. LEVTOCO^CmJS, Biippeil. 



Animal; proboscis elongated, retractile; te^itacles two^ smooth, 

 triangular, jointed internally at the base, and hearing the eyes 

 externally in the middle ; disc middling, no operculum ; mantle 

 circidar at the edge, loithout any siphonal appendage, a little 

 produced on the left side ; branchial orijice rather large. 



Shell ; thin, pellucid, nearly globose, spire depressed, rather ob- 

 solete ; aperture large, suhoval, extremities turned contrariwise, 

 margins disjointed, right margin thin, a little expanded ante- 

 riorly ; umbilicus none, truncated anteriorly, contorted. 



Such are the descriptions of Leptoconchus recorded by Dr. Riippell, in liis 

 communication to the Zoological Society of London in September, 1834!- 

 It is alHed to the Magilus, with this difference, the margins of the aperture 

 are not united, and by reason of its dwelHng in exposed cavities of madre- 

 pore, forms no extended tubular growth. 



" The colour of the shell," says the learned traveller, " w^hich constitutes 

 the type of this new genus, is constantly a shghtly sordid milk-white. It 

 is sulcated externally by numerous longitudinal undulated closely-set lines, 

 the outer whorls encroacliing on the spire of the earHer ones so as almost 

 to obHterate it. Individuals of all ages have the shell thin and fragile, and 

 constantly occur imbedded in the calcareous mass of polypes, having a com- 

 munication with the sea by only a moderate opening. The animals of 

 Magihis and Le2)toconchus are distinguished by the presence and absence of 

 an operculum, and by the difl'erence in the proboscis ; the siphon of the 

 former, moreover, does not occur in the latter,""^ 



Dr. RiippeU suggests that Leptoconchus might be arranged in the vicinity 

 of lantldna, I cannot, however, subscribe to this opinion, the habits and 

 structure of these moUusks being so totally dissimilar. 



Figure. 



Leptoconchus striatus. PI. 4. Kg. 20. Showing, a and I, back and 

 front view of the shell ; c, as it appears imbedded in a mass of coral. — 

 ¥rom Mr. Cuming's collection. 



* Pro Zool. Soc. 1834. p. 105. 



