5° 



Stat. 95. 5°43'.5 N., ii9°4o'E. Sulu Archipelago. 522 Metres. Stony bottom. i Fragment. 



Stat. 178. 2°4o' S., I28°37'.5E. Ceram Sea. 835 Metres. Blue mud. 2 Spec. 



Stat. 300. io°48'.6S., i23°23'.iE. Timor Sea. 918 Metres. Fine grey mud. ± 23 spec. 



Diagnosis. Shell smooth, slender, rather strongly curved, three.sided, flattened on the 



inner, rounded on the outer curve. The inner or convex side is defined by 



( \ lateral angles, rather sharp near the apex but becoming anteriorly more rounded. 



Apex with a wide shallow notch and a tubular (in sonie specimens rather lon<') 

 Fig. 24. ^ _ _ V i ,^; 



Section neai- the .->pex appendage. Somctimes the tube is also notched. Great many specimens have 

 the apex broken and it is then visible on the section that the inner margin is 

 thickened, while the outer margin is thin edged. They enclose a round opening. Anterior aperture 

 trigonal, with rounded corners. Shell brilliantly white, transparent in live state, porcellanous 

 when dead. Alany superficial growth striae with here and there a deeper circular line. 

 Length 46 mill., diam. at aperture measured along the inner margin 3 mill. 



D i s t r i b u t i o n. Bay of Bengal in 597 fms. (Investigator). 



R e m a r k s. This shell is nearly allied to the fossil Gadilina triquetra Br. of the lower 

 Miocene of Piedmont (Sacco, I Moll. del. Piem. e delle Lig. Pt. XXII, p. 113, Tav. X, figs 

 35 — 43) and to Dentalium trigonale K. Martin (Samml. Geol. Reichsmus. Leiden, i''^ Serie, 

 Bd III, 18S3 — 'è"i, Tab. X, Fig. 192) of the Java Tertiary. 



The Siboga-specimens show the characters of D. insolititiii rather strongly accentuated, 

 but after comparison with the types in the British Museum, I find the difference to be too small, 

 to justify a separation. Gadilina triqji-etra Br. obligingly sent to me by Prof. Sacco from the 

 ]\Iuseum of Torino seems to be an intermediate form between insolitjtiii and stapes. 



59. Dentalium stapes n. sp. PI. V, figs 16 — 20. PI. VI, figs 79, 81, 83. 



Stat. 212. 5°54'.5S., 120° 19'. 2 E. Banda Sea. 462 Metres. Fine grey and green mud. ± 35 Spec. 



Diagnosis. Shell moderately curved, finely tapering, threesided, sharply keeled on the 

 convex, flattened on the concave side. Keel on the outer curve high and 

 narrow, with flat lateral walls; wall on the inner curve (seen on a transverse 

 section) very faintly convex and sometimes slightly sunken between the 

 F'g- ^5- protruding lateral angles (at least near the apex). Toward the anterior aperture 



Anterior aperture and 



section near the apex tli^ keel and augles become blunter, the surface of the sides more convex, 

 of D. stapes. j^j^jj. jj.jg trigonal form remains clearly noticeable to the end. Apex extremely 



attenuated, very slightly notched, and sometimes with a supplemental tube. In some much 

 attenuated specimens the apex is microscopically, longitudinally striated. The top has the shape 

 of a horse-shoe, the anal orifice being pear- or egg-shaped, while the inner margin is flat and 

 thick-edged, the outer margin arched and thin-edged. Anterior aperture decidedly trigonal. 

 Minute growth striae, close and superficial with .some deeply incised lines. 

 Length 47 mill., diam. of aperture, measured along the inner margin, 2,1 mill. 

 Length 44 mill., diam. of aperture, measured as above 2,4 mill. 



Remarks. D. insolituiii and stapes are nearly allied. Anteriorly the shells are much 



