55 



The smooth specimens alone deserving the name of lacteum it remains a question whether 

 this species is really well defined, a question however I have no means of answering. 



*65. Dentaliiiin bisiimatuiii Andre. PI. II, fig. 29. 



1896. Dentaliitm bisinuatuni Andre, Revue Suisse de Zool. et Ann. du Mu.s. d'Hist. Nat. de 



Geneve, IV, fasc. 2, p. 397, pi. 17, fig. 9. 



1897. Dentalium bisinuatiim Andre. PiLSBRY & SHARP, Man. of Conch., vol. XVII, p. 108, 



pi. 19, figs 7, 8. 



Diagnosis. Shell conic, perfectly circular in transverse section, little curved, thin, 

 translucid, glossy of a yellowish corneous color ; with oblique regular, fine transverse striae. 

 Aperture circular, a little oblique ; peristome sharp, irregular. Apex with two small notches, one 

 ventral, the other dorsal, a Httle deeper than the former. 

 Length 33,5, diameter of the aperture 3 of apex 0,5 mill. (P. & Sbi. from Andr^). 



Distribution. Amboyna. 



66. Dentalium banale n. sp. PI. VI, fig. 30. 



Stat. 300. io°48'.6S., 123° 23'.! E. Timor Sea. 918 Metres. Fine grey mud. 2 Spec. 



Diagnosis. Shell evenly and moderately curved, circular in section, pretty strong. No 

 sculpture except for many close irregular and rather conspicuous growth striae with here and 

 there a deeper incised line. Colour white or bluish white. Apex simple, without slit or notch, 

 circular, with thick walls, in which the concentric structure of the shell is clearly visible. In both 

 specimens the shell's inner layer projects a little above the rest,* faintly indicating the existence 

 of a supplemental tube. Anterior aperture circular with thin strong edges, Httle oblique. 

 Length 39 mill., diam. of anterior aperture 2,9 mill., diam. of apex i mill. 

 Length 43 mill., diam. of anterior aperture 3,2 mill., diam. of apex 1,3 mill. 



Remarks. This species hardly has any distinctive characters. For its lack of sculpture 

 I have placed it in the subgenus Laevidentalituu ^ though it is possible that it is related to 

 species of the subgenus Plagioglypta. The deeply incised circular lines remind one of the 

 "segments" in D. scinitrachcatitm. Both specimens obtained by the Siboga are much eroded, 

 and show many white opaque patches, with here and there a dark brown deposit in more 

 deeply eroded parts. 



Subgenus Plagioglypta Pilsbry. 



Plagioglypta Pilsbry in Textbook of Palaeontology and PiLSBRY & Sharp, Man. of Conch., 

 vol. XVII, p. xxxi. 



Shell circular or elliptical in section, without longitudinal sculpture, with clo.se and fine 

 obliquely encircling wrinkles throughout or on the posterior portion. Type D. iindulatuni 

 Munster (P. & Sh.). 



This group is especially characteristic of the early and middle Mesozoic, and it is therefore 



