MOLLTJSCA OF THE * CHA.LLEN"GEE ' EXPEDITION. 



521 



4. SlPHODENTALIUil TETRASCHISTUM, W, 



St. 113 A. Sept. 2, 1873. Anchorage off Fernando Noronha. 

 7-25 fms. 1 specimen. 



Sliell. — Cylindrical, tapering, bent and attenuated from about the 

 middle to the apex ; toward the mouth very slightly contracted. 

 It is rather strong, and has the dull gloss and white translucency 

 of a quill. There are two opaque bauds round the apex. 

 Sculpture, There are traces, exceedingly faint, of fine close- 

 set striae, which run elliptically round the shell on the lines of 

 growth, and in some lights there Is just a reflection as of some 

 sort of remote longitudinal texture (very like that in S. ( Dis- 

 chides) hifissum^ "Wood). The edge of the mouth slopes back- 

 wards very obliquely from the concave to the convex side of the 

 shell ; it is thick, and all round it is smoothly rounded off. The 

 apex projects on the convex side of the shell, and is split by 

 four opposite, shallow, unequal, irregular, rough-edged, gaping 

 clefts, so arranged as to leave the teeth at the convex and con- 

 cave curves and at the two sides. The bands round the apex 

 are two narrow callus-like ribs. L. 0"298. B. at mouth 03, 

 at broadest 0*035, at apex 0-017. 



This species approaches nearest to Siphodentalium (Dischides) 

 lijlssum, Wood, but that species has only two, and these lateral, 

 narrow, deep, and regular, posterior clefts ; its mouth is squarely 

 cut off with a thin and jagged edge ; its shell is very little 

 contracted at the mouth, and contracts slowly but constantly all 

 the way to the apex; is also longer, more bent, and thinner. 

 S. lofotense, Sars, and aS^. vitreum, Sars, which, have the four pos- 

 terior clefts, are totally unlike in texture and in form. 



5. Siphodentalium dichelijm, W. (hixn^os.y 



July 29, 1874. Levuka, Fiji. 12 fms. 1 specimen and 2 

 fragments. 



Shell. — Long, slightly swollen at about three fifths of its length ; 

 the swelling bulges on the concave curve, but the convex curve 

 is uninterrupted ; between these two curves it is compressed 

 by one sixth of its breadth, a little contracted in front, bent 

 and attenuated toward the apex ; thin, brilliant white, almost 

 hyaline, with a few minute, transverse, curdy streaks, but 

 weathering to opaque. There is an opaque band round the apex . 



LINN. JOURN. — ZOOLOGY, VOL. XIT. 38 



