PHYLOGENY OF FUSUS AND ITS ALLIES. 69 



shell marks the beginning of a new series, the variation has not as yet 



become pronounced enough to enable one to state its characteristics 



precisely. 



FUSUS MARMORATUS var. ,?. 



Tiiis variety differes from the preceding in being more angulatcd in 

 the young, when the whorls are rather strongly bicarinatc. The 

 shoulder is flat, though strong spirals detract somewhat from the flat 

 apearance. Intercalated spirals appear on the fourth or fifth whorl, 

 and later become compound. In the adult whorls the ribs generally be- 

 come obsolete, first fading toward the sutures and later wholly dis- 

 appearing except on the keel, where they produce the nodules. The 

 spirals are sharp and somewhat serrated by the lines of growth. 



There is considerable variation due to the earlier or later sup- 

 pression of the ribs. Sometimes the angulation of the early whorls 

 is less strongly marked, and then the specimen resembles the typical 

 F. uiaruioratus. In some specimens the ribs disappear before the adult 

 stage is reached, and in the majority of specimens seen the last portion 

 of the last whorl is keelless as well. 



From the material so far seen two types of variation may be dis- 

 tinguished. The torcunuis type retains the ribs towards the end, where 

 they are represented by the nodules on the keel, while the coins type 

 has the last whorls ribless and without tuliercles on the keel. If the 

 present variety is considered as a species, the several mutations, which 

 mark distinct stages of development, must be considered as distinct 

 varieties. In this, as in all the previous cases, acceleration is responsible 

 for the production of these mutations, and it will thus be seen that, 

 although the actual difiference between this shell and the normal F. 

 inarnioratus is not so very great, being perhaps mainly what may be 

 called a provincial mutation {i. c, a variety developed in a separate 

 province, cut ofit from the mother form), it has nevertheless begun to 

 develop an independent series. 



Judging from Kiener's figure the type of F. viulticarinatiis has a 

 longer canal, and has only simple spirals. It is also less spinose in 

 appearance than this variety, and the coloring is more uniform. 



A rather striking specimen of this species is in the collection of the 

 Boston Society of Natural History (228). The early whorls are round 

 and the ribs rather narrower than in the preceding specimens. Angula- 

 tion and intercalated spirals appear in the fourth whorl. The ribs are 

 rather widely separated for this species. The shell is somewhat 

 corroded, and does not show sharp surface characters nor coloration. 

 Just below the suture on the shoulder the whorl is marked by a de- 

 pressed band, which in the last whorl becomes a slightly depressed 

 canal or canaliculated interspiral space, containing two secondary spirals. 

 In the last part of the last whorl the ribs are in the form of vertical 



