112 PIIYLOGENY OF FUSUS AND ITS ALLIES. 



The ritgosiis stage is succeeded by a daiiicriacciisis stage, which is 

 usually short and consists of rounded whorls, free from ribs, but 

 ornamented by strong spirals. With the disappearance of the spirals 

 the dameriacensis merges into the conjunctus stage, which is, as a rule, 

 strongly developed in this species, even though the dameriacensis stage 

 should be absent. This is particularly the case in the varieties with a 

 short or obsolete rngosus stage, the suppression of which leaves room 

 for the development of the dameriacensis and conjunctus stages (pi. XI, 

 fig. 7). When, however, the rngosus stage persists, the dameriacensis 

 and conjunctus stages are abbreviated, the parisiensis stage following 

 soon after the rngosus (pi. XI, fig. 9; pi. X, fig. 10). In this 

 respect fig. 8 of pi. XI is intermediate between fig. 7 and 9 of 

 the same plate. In some accelerated individuals the rngosus stage 

 is almost eliminated, but the ribless, spiralled dameriacensis stage is 

 well marked. This is followed by the parisiensis stage, the conjunctus 

 stage being eliminated. In the early stages of the more characteristic 

 specimens of this species the subsutural concavity on the upper part 

 of the whorls, which is characteristic of C. conjunctus, is well developed. 



In the adult or ephebic stage, a sutural shelf is developed and the 

 aperture contracts until the side of the whorl is parallel to the longi- 

 tudinal axis of the shell. The body-whorl thus becomes cylindrical. 

 This is the parisiensis stage, and when it occurs in conjunction with 

 the conjunctus and rngosus stages we have a typical C. parisiensis. 

 The dameriacensis stage may or may not be present, according to the 

 degree of acceleration which the shell has experienced. Variation 

 is also produced by the unequal acceleration of different stages of 

 the shell, one or the other of which may be developed at the expense 

 of the adjoining one. Thus a number of varieties are produced which 

 shade into each other and connect this species with others of this series. 



In an injured or gerontic specimen (M. C. Z. loSi, pi. X, fig. 10) the 

 last portion of the last whorl assumes again the features of the con- 

 junctus stage. The shoulder disappears and the lines of growth be- 

 come lamellose and crowded while the whole whorl becomes more 

 globose. Similar features are seen in injured specimens of all sizes. 

 The shoulder expression of the whorl below the suture is not at once 

 regained, but a rounded indefinite form, lying between C. parisiensis 

 and C. conjunctus is produced. One specimen only has been observed 

 (M. C. Z. 1093) i" which the last part of the last whorl, of a moderate 

 sized specimen had a projecting shelf similar to that of C. scalans. The 

 specimen is from Auvers. 



Localities: Chaumont (M. C. Z. /075, Agassiz) ; Parnes (M. C. Z. 

 1075, Baucault, 27753, Duval) ; (arignon (M. C. Z. 1079, 108 1, Duval; 

 Acad. Sci. 8025, 6892) ; Mt. St. George (Cossmann) ; Chaumery (M. 

 C. Z. 1076, Koninck, 27787) ; Cuise (M. C. Z. 1095) ; Paris (M. C. Z. 



