PIIYLOGENY OF FUSUS AND ITS ALLIES. II5 



Strongly accelerated variety is shown in fig. 3, pi. XII, and a slightly less 

 accelerated one in fig. 2 of the same plate. In the first of these speci- 

 mens the protoconch which consists of three and a half volutions is 

 followed by a smooth and spirally striate rounded whorl. This and 

 the succeeding whorls embrace each other closely, thus producing a 

 short and swollen spire. Faint undulations occur on some of the 

 whorls but there are no ribs. There are two spirally striate whorls 

 without shelf (dameriaccnsis stage). The shelf appears in the third 

 whorl. Toward the end of the fourth whorl the spirals have become 

 obsolete and the whorl changes from rounded to cylindrical. A very 

 pronounced posterior canal is developed. In fig 2 the whorls embrace 

 in a similar manner but about two whorls of the rugosiis stage (ribbed) 

 are retained. With the disappearance of the ribs the sutural shelf 

 makes its appearance, and later the spirals disappear. A suhtnbcrculosus 

 and a tuhcrculosus stage is produced. This is followed by a short 

 parisicnsis stage. Fig. i of plate XII represents another accelerated 

 variety. Here the shelf appears while the ribs are still represented by 

 undulations (this may be called a rugoso-fuberculosus stage). This is 

 succeeded by a very short tiiberculosits stage (the spirals having dis- 

 appeared with the ribs), and this quickly merges into the parisiensis 

 stage. The rugosus stage is very persistent, there being at least four 

 complete volutions. Fig. 4 of plate XII represents an immature C. 

 parisicnsis which has scarcely passed beyond the conjunctiis stage. 

 The last part of the wdiorl shows a deformation. 



A strongly marked variety from Paris is shown in fig. 8 of plate 

 XII. This might well be considered a distinct species. The spire is 

 short and the last whorl is thick, condensed and with a long anterior 

 canal. The protoconch is furnished with a few narrow vertical riblets. 

 These are followed by the normal ribs of the conch wdiich are character- 

 istic of about three volutions. A sutural shelf is formed, before the 

 ribs fully disappear, giving a short rugoso-tuhcrcnlosus stage. A short 

 subtiibcrculosus stage (like tnbcrculosns but with spirals) follows, and 

 is in turn succeeded by a smooth tiiberculosus stage. These three 

 shelved and round-whorled stages are very short, and soon give way to 

 the cylindrical whorls of the parisiensis stage. Thus the present variety 

 of C. subscalaris consists of a rugosus, a short rugoso-tubcrciilosus, a 

 short subtiibcrculosus, a longer tiiberculosus and a well-developed 

 parisiensis stage. 



Figs. 5 and 6 of plate XII show young specimens of accelerated 

 varieties of perhaps this species, but more probably of C. scalaris. In 

 fig. 5 the ribbed stage is absent altogether, having been dropped out 

 (acceleration by elimination). The whorls are all round and spirally 

 striate, intercalated striae arising in the third whorl. The sutural 

 shelf appears while the spirals still continue {subtuberculosus stage). 



