Occasional Papers of the Museum of Zoology 87 



evenly convex; suture oblique, shallow except near the apex. 

 Sculpture of last whorl: growth-wrinkles fine, regular and 

 thread-like, vaguely and very lightly crenulated by a few, 

 spiral striations. Aperture: elongate-ovate, witli long axis 

 slightly oblique to that of shell. Peristome : columellar trunca- 

 tion slight in adults but relatively prominent in the embryonic 

 shell; parietal lamella compressed, present as a thin lamella 

 on the central axis of the last but dying out on the penultimate 

 whorl of the adult, present as a fine, internal thread in a young 

 shell of 5 1/2 whorls, not developed in embryonic shell (fig. 

 xvi-58). 



Radula (fig. xiv-53): C/3, L7/3, M4/+(10/4+): or 

 21-1-21. Very similar to that of Opeas heckianum {cf. 1923 ; 

 this series, no. 135, fig. 1-6), but the cusps of the inner laterals 

 are broader and heavier ; the teeth in each transverse row de- 

 crease more rapidly in size towards the outside; and, in the 

 marginals, the entocone (first), ectocone and mesoeone become 

 subdivided into minor cusps (all usually tricuspid in Opeas). 



Jaw (fig. xvi-64) : thin, transparent, arcuate, crossed by 

 numerous, well-impressed lines, which separate rounded, gran- 

 ulate riblets. 



Measurements 



alt. maj. diam. alt. apert. diani. apert. whorls 

 embryo (fig. 58) 1.8 60(1.07) 58(1.04) 53(0.55) 21^4 



largest, B6 (fig. 61) 11.5 20(2.33) 22(2.57) 54(1.39) 9 



Smith (1898) 9.0 25(2.25) 22(2.0 ) 8 



As Smith (I.e.) was apparently unfamiliar with the de- 

 scription of N. gloynii, he did not differentiate the two species. 

 As a result, his species would be unrecognizable without the 

 locality. The absence of the parietal lamella in the embryonic 

 shell indicates that N. harterti is more distantly related to N. 

 gloynii and N. scopulorum than they are to each other. The 

 specimens from the northern localities on Bonaire (my meas- 

 urements and figures) average slightly larger than do those 

 from the more southern stations (probably typical harferti). 

 Although considerable search was made for it, this species was 

 not obtained on Klein-Bonaire. 



