6o 



Diagnosis. Shell slender, tapering, rather strongly arcuate in young specimens, straighter 

 in adults; cylindrical, the length about lo times the greatest diameter. Surface very glossy and 

 smooth, growth lines hardly perceptible. Colour near the apex reddish, sometimes deeply flesh- 

 coloured and fading to white or yellowish white near the anterior aperture. Anterior aperture 

 circular, slightly oblique, peristome thin-edged. Apex with a deep narrow slit on the convex 

 side, continuing in an internal groove, its length contained about 4 — 5 times in length of shell. 

 Length 36, diam. of apert. 3,4, length of slit 4,5 mill. 

 Length 32, diam. of apert. 3,1, length of slit 7,5 mill. 

 Length 30, diam. of apert. 2,5, length of slit 7,5 mill. 



Distribution. Naples. Sicily (Monts). 



Remarks. Resembling strongly D. rudesccns Desh. ') and occurring in the same localities 

 with that species, tenuifisstiin was at first treated as a variety of rubescens. I have hesitated 

 before recepting Mr Pilsbry's view of treating them as distinct .species. It is a fact that but 

 for the long linear slit in ienuifissuin both species bear a marked resemblance to each other. 

 Moreover I find that there is in the specimens of D. rubescens^ obligingly sent to me by Mr 

 JouBiN from the Mus. d'Hist. Nat. de Paris, a long internal groove, ending near the apex in 

 a small triangular notch. This fact had already been mentioned by Deshayes in his Monograph. 

 But also in tcmiifissum the slit continues anteriorly in an internal groove, exactly like the one 

 in rubescens. The only difference therefore which remains between both species is that in 

 tenuifissum the groove is posteriorly (near the apex) open, while in rubescens it seems to be 

 always shut. No specimens of the kind of rtibescens were obtained by the Siboga and it is 

 therefore that I have treated them as distinct species. 



II Family. SIPHONODENTALIDAE. 



Scaphopoda having the foot either expanded distally in a symmetrical disk with crenate 

 continuous edge with or without a median finger-like projection, or simple and vermiform, 

 without developed lateral processes. The shell is small and generally smooth, often contracted 

 towards the mouth. Other characters essentially as in Dentaliidae. (P. & Sh.). 



Key to genera of Siphonodentalidae. 



I. Shell largest at aperture, thence tapering to apex. 



a. Longitudinally ribbed, angular in section at least near the apex. Entalina . . . p. 61 

 rt;'. Smooth; circular or subcircular in section throughout . . . Siphonodcntaliuin. p. 64 

 II. Shell m.ore or less swollen near the middle or anteriorly, contracting 



toward the aperture as well as tapering posteriorly .... Cadulus . . . p. 65 



i) V. rubescens Desh. Mem. Soc. Hist. Nat. Paris, II, p. 363, pi. 16, fig. 23 — 25 (1825) and Pilsbry & Sharp, Man. of Conch, 

 vol. XVII, p. 105, pi. 19, fig. 2 (1897). 



