ORTMANN : TERTIARY INVERTEBRATES. 231 



face with spiral striae and longitudinal ribs, this sculpture becoming quite 

 indistinct on the last whorl. In large individuals the last whorl is often 

 quite smooth except for growth-lines. Spiral sculpture very variable, 

 sometimes strongly developed, in other cases weak, or entirely disappear- 

 ing. Longitudinal ribs also variable ; in most cases distinct on the upper 

 whorls, but not reaching the upper suture. On the lower whorls these 

 ribs disappear, being represented, in many cases, by slight and indistinct 

 swellings on the shoulder, and disappearing in very large shells entirely 

 on the last whorl. Mouth elongate. Columella with three plaits, the 

 uppermost sometimes very slightly developed. 



Measurements: Height, 186 mm; diameter, 79 mm (complete, except 

 for apex). Height, 70 mm ; diameter, 27 mm (complete, young). 



Remarks: As v. Ihering points out, this species is well characterized 

 by the elongated mouth, which is comparatively much longer than that of 

 V. triplicata and allied forms, and, further, by the tendency of the longi- 

 tudinal ribs to disappear on the lower whorls, the last whorl, in large 

 individuals, being quite destitute of ribs. 



V. Ihering has sent us the lower half of a large specimen of this spe- 

 cies, which agrees well with our large individuals. 



We possess a number of small individuals, which agree in form. Two 

 of them show the apex: it is distinctly of the Caricella-type of the Sca- 

 phelloid-series (Ball, 1890, b, p. 70). (See our plate XXXVI, fig. 

 !*.) 



One individual (plate XXXVI, fig. i') shows the spiral striae very 

 strongly developed, even on the beginning of the last whorl. Specimens 

 like this, when only parts of the surface of the lower whorls are preserved, 

 which do not possess any longitudinal ribs, may have been taken by v. 

 Ihering for V. alta. V. Ihering himself says that his V. alta and dor- 

 bignyana are similar in form (which is really not correct, the true V. alta 

 of Sowerby from the Navidad beds having a much shorter mouth), and 

 that he had only very poor material of his V. alta (only one individual 

 showing remains of the shell). Since the absence of longitudinal ribs in 

 V. alta is the only difference between v. Ihering's V. alta and V. dor- 

 bignyana, and since these ribs also tend to disappear on the lower part in 

 V. dorbignyana, and, indeed, do so complefely on the last whorl, it is 

 quite possible that v. Ihering's V. alta corresponds to such specimens of 

 V. dorbignyana as is represented in our figure. 



