16 ANNAL8 NEW YORE ACADEMY OF SCIENCES 



The youngest volution available for study is 1.9 mm. in diameter, and 

 it is probable that several volutions have been broken away above this. 

 It has a sharply angled outline, with the most projecting portion slightly 

 above the middle of the whorl. It is ornamented with three strong, con- 

 tinuous spirals, the uppermost of which is stronger than the others. Two 

 finer spirals are present on the shoulder, and one is visible just above the 

 suture. The entire surface is roughened by exceedingly fine, thread-like 

 costse crossing the spirals at right angles. They are too fine and too 

 closely set to appear like ribs, and ribs of the usual kind are entirely 

 absent at this stage. The ornamentation remains similar in type, with 

 the intercalation of finer spirals between those already existing, until the 

 sixth volution, on which widely spaced ribs appear. At this stage the 

 volution is about 6 mm. in diameter. The fine spirals increase rapidly 

 in number, and on the later volutions the primary spirals seem to be 

 made up of clusters of finer spirals with the clusters separated by deep, 

 smooth grooves. At about the ninth volution the median of the three 

 spirals becomes almost as strong as the uppermost spiral, so that for two 

 or three volutions the obtuse angled outline of the whorl characteristic 

 of Cerithium is suggested. The upper spiral, however, soon becomes 

 again the most prominent one, and this tendency increases until, on the 

 body volution, this spiral forms the margin of very large, blunt, flat- 

 topped nodes, with the ribs nearly obsolete above and below them. On 

 the late whorls the finer spirals are sometimes confluent and the former 

 cluster becomes a broad, flattened ridge defined by a narrow groove on 

 either side. The body volution below the nodes bears three broad nodose 

 spirals. 



The aperture is oval, with the outer lip flaring and thrown into strong 

 folds by the coarse spirals of the outer surface. The lowest of the spirals 

 on the body whorl is sometimes produced to such an extent that it forms 

 a projecting tooth which crosses the opening of the canal. The inner 

 lip bears a strong callus with a prominent tooth near the posterior portion 

 of the aperture. The siphonal canal is broad and deep and slightly bent 

 backward. 



Horizon and localities : Recent. Moluccas, Philippines, Indian Ocean. 

 No. 40203, Columbia University collection. 



The yoiini!: indivirlual figured is from the exhibition collection of the Museum 

 of Comparative Zoology. 



Eemaeks: Although the adult of this species bears some resemblance 

 to Cerithium tuberosum, its development is unlike that of any species of 

 Cerithiidas studied. The formation of a distinct shoulder so long before 

 the appearance of ribs and the presence of the fine costae crossing the 



