1894.] LAND-SHELLS FROM THE SAMUI ISLANDS. 153 



Operculum cyathiforme, suhtestaceum , intus profundissime cylin- 

 drico-excavatum, Icve, nitens, extns hreviter ej/Undricum, tuni 

 semujlohosum, apice suhplano, anfr. 12 marghiihus lamellatim 

 elevatis, in interstitiis oblique striati. 

 JDiam. maj. 24'5, 7nin. 18, alt. 13'0 ; oj)ercidi diam. 6, alt. 4 



millim. 

 This very interesting form differs from all known species of 

 Hhiostoma in the want of a sutural tube, whilst the operculum is 

 quite typical. This is another proof that the formation of a tube, 

 which is but an extreme development of the " wing " at the peri- 

 stome of Eucydotus and Pterocijdus, is of less systematic value than 

 is generally supposed. The classification of operculate shells will 

 have ultimately to rely upon the structure of the operculum chiefly, 

 if not exclusively. 



24. Cyclophorus malayanits, Bens. 



Whilst Prof, von Martens is quite right in combining the so- 

 called C. malayanus of the ' Conchologia Indica ' and of Reeve with 

 the very variable C. aurantiacus, Schum. (Journ. Linn. Soc, Zool. 

 xxi. 1887, p. 159), I believe with him that the true C. malayanus, 

 Bens., of Pulo Penang is a distinct species. A fine large Cyclo- 

 ■phorus of the Samui group I consider to belong to it, although I 

 cannot compare typical specimens. My largest example measures 

 48 by 39 millim. 



25. Cyclophorits diplochilus, sp. nov. (Plate XVI. fig. 24.) 



T. pro genere anguste umhilicata, suhdepresse turbinata, solida, 

 transverse leviter striatula, lineis spiralibus rugulosis decussata, 

 pallide corneo-fusca, tceniis interruptis castaneis, interdum 

 strigis castaiieis jiammulatis picta. Anfr. 4| , perconvexi, ad 

 sut^iram subplanati ; ultimus antice vix descendens. Apertura 

 sat obliqua, circidaris ; peristoma duplex, externum album, late 

 expansum, revolutum, rnarginibus callo junctis, columellari dila- 

 tato ; internum aureum aut auraniiacum,valde nitens, continuum, 

 late expansum, margine dextro valde dilatato, crassum, quasi 

 mulii2ylicatum, sulco ah externa separattim. Operculum normale. 

 Diam. maj. 38, min. 28, alt. 31 ; diam. apert. c. perist. 24, intus 



14 millim. 

 Porma minor : diam. maj. 30, min. 22'5, alt. 25 ; diam, apert. 18, 



intus 11 millim. 

 At first I believed this fine shell to be C. cucullatus, Gld., of 

 Mergui, of which no figure has been published, and which v. Mar- 

 tens in his able paper on the Mergui Archipelago does not 

 mention. According to the diagnosis of Gould's species as given 

 by Pfeiff'er (Mon. Pneum. suppl. i. p. 44), however, there appear 

 to exist sufficient differences to justify the separation of the two 

 forms specifically. C. cucullatus is considerably smaller, white, 

 the last whorl subangulate, the columellar margin not dilatate, the 

 outer peristome is only called " reflexiusculum," whilst in my 

 species it is strongly recurved, &c. Otherwise the formation of 



