20 PHYLOGENY OF FUSUS AND ITS ALLIES. 



FUSUS HAITENSIS Sowerby. 



1850. Fusus haitensis Sowerby, Quart. Journ. Geol. Soc, vol. 6, p. 49. 

 1876. Fusus henekeni van haitensis Guppy, Quart. Journ. Geol. Soc, vol. 32, p. 

 524, pi. 28, fig. 2. 



This species is like the preceding except that the last two whorls 

 show a flattening of the shoulder and a peripheral angulation. The 

 ribs also become obsolescent towards the sutures, but remain strong on 

 the periphery, thus producing a crude nodulation. The last two 

 whorls are also somewhat more drawn out, so as to expose more of the 

 preceding w-horl. Intercalation begins early. In the specimens ex- 

 amined the apex was imperfect, and intercalated spirals were present 

 on the earliest whorl preserved. 



In the specimen figured by Guppy at least four angular whorls 

 occur; the ribs continue to the last whorls, though prominent only on 

 the periphery. The keel is sharp and strongly developed, the shoulder 

 flat, and the spirals compound. The shell is a parallel to F. torctuniis 

 in the F. coins series. 



This species is an accelerated F. hcnckcni, but with constant char- 

 acteristics, which show that this is not a case of individual gerontism. 

 It is rather phyletic, and hence of specific value. From this it appears 

 that this species is not to be united with the preceding one, as has 

 been done by Guppy, Gabb and others. 



Locality: San Domingo (Phil. Acad. Sci.). 



Horizon: Upper Oligocene (occurring with the preceding). 



Recent Species. 

 FUSUS EUCOSMIUS Dall. 



1889. Fusus eucosmius Dall, Blake Moll., p. 167, pi. 35, fig. 5. 



This species is more compact and shorter than the Chinese F. tur- 

 ricida, which it resembles closely. The protoconch has a more com- 

 pact appearance, the ribs in the latter portion being somewhat stronger 

 than those in F. tiirricnliis. The protoconch ends in a strong varix. 

 Intercalation begins on the fifth or sixth whorl. The three central 

 spirals generally become prominent in the young shell,- sometimes as 

 early as the second or third whorl. The middle one of the three is 

 always the strongest. A slight flattening of the shoulder accompanies 

 the strengthening of the central spirals, this feature being most marked 

 in the adult. The shoulder spirals do not increase in strength in the 

 same proportion that the central ones do, and hence there is a marked 

 difference between these two sets in the adult. In the adult the ribs 

 are generally more bulging than is the case in F. tiirriciiliis. The 

 aperture is often strongly contracted, and a sudden enlargement like 

 a strong varix has been observed in some specimens. 



I 



