I04 PHYLOGENY OF FUSUS AND ITS ALLIES. 



Paris, T. II, pi. 74, fig. 21. 1824. Clavilithcs Jongccz'us Lam. var. 

 of authors generally. C. deforinis var. Cossmann. 



THE GENUS CLAVILITHES Swainson. 



This genus was instituted by Swainson in 1840,* as a substitute 

 for ClavcUa, which he had established a few years earlier (1835"}") for 

 Fitsus longcuz'us Lamarck (Deshayes) {=F. parisicnsis Mayer-Eymar) 

 and allied types. The later generic name would not hold, were it not for 

 the fact, apparently unknown to Swainson, that Clavella was used by 

 Oken in 181 5 for a crustacean. Swainson included Fiisus noce in his 

 genus, a practice carried out by every subsequent writer. That species 

 is, however, strikingly distinct from F. longcrznis of Lamarck and 

 Deshayes, and is here separated under the generic name Rhopalithes. 

 Swainson's description leaves no doubt as to which species belong to 

 his genus, for he gives the characteristics of F. longcevus {F. parisiensis 

 May.) and not those of F. noce. 



The protoconch of this genus is very striking, and is distinctive, 

 though there are other genera, apparently not very closely related to 

 this genus, which have similar or perhaps even identical protoconchs. 

 The first whorl of the protoconch is depressed and naticoid, with a 

 minute apical portion. The whorl gradually enlarges, but after the 

 first volution the proportional increase in size is much less, so that the 

 whorls produce a nearly cylindrical protoconch. There are from two 

 and a half to four whorls, thus giving the protoconch a distinctly 

 papillose appearance. The protoconch is umbilicated and very gen- 

 erally contains from one to several septa. There is no final varix, and 

 the line of separation between protoconch and conch can not generally 

 be indicated. In some specimens (fig. 15) a sharp line marks a cessa- 

 tion of growth, but whether that is the end of the protoconch or merely 

 a temporary interruption in the building of the protoconch is not clear. 

 The fact that this line is not found in all specimens suggests that it is 

 only an individual characteristic and does not necessary mark the end 

 of the protoconch. This view is strengthened by the fact that similar 

 lines occasionally occur on other parts of the protoconch, where they 

 mark a slight interruption of growth. Sometimes a slightly wrinkled 

 appearance is produced by these lines, which give a faintly ribbed 

 aspect to the protoconch in places. A few simple smooth ribs occur 

 before the normal ribs of the conch appear, and between these smooth 

 ribs are generally to be found faint revolving lines. These do not, 

 however, aflrect the ribs. It is a question difficult to answer whether 

 this portion belongs to the protoconch or to the conch. As the change 

 is not a very abrupt one we may assume that the embryonic stages 



* Swainson, " Treatise on ^Malacology,"' p. 304, p. 90. 

 t Swainson, " Elements of Conchology." 



