38 PHYLOGENY OF FUSUS AND ITS ALLIES. 



to assume the F. closter characters more readily, that species being the 

 more characteristic representative of tlie series in American waters. 



When the tubercles continue throughout in the West Indian species, 

 the characters are generally those of the Philippine shells. The fine 

 striae occurring between the spirals of the Philippine shells also occur 

 on those from the West Indies. The shoulder is often more sloping 

 in the American shells, thus giving them a more slender and elongate 

 appearance. A slight but broad concavity exists on the upper portion 

 of the shoulder. There is some variation of the apical angle, which, 

 however, often equals that of typical Philippine shells. 



The tubercles generally become confluent into a well-marked keel, 

 which is sometimes undulating, and sometimes smooth, and occupies 

 from a fragment of a volution to two volutions or more. In almost 

 all cases, the keel disappears towards the end, a uniformly rounded 

 whorl, furnished only with spiral lines, alone remaining. 



It will thus be seen, that whereas the toreumus type is the best 

 represented type in Philippine waters, in American waters this is almost 

 entirely replaced by the coins type. The longicaudus type, represented 

 by F. closter, is most characteristic of the West Indies. It is there- 

 fore most probable that the American species were derived from the 

 Philippine species, since the latter are the more primitive. 



Localities: Philippine Islands (B. S. 260; M. C. Z. 892; Acad. Sci. 

 Wilson coll.) ; Isle of Margarita W. I. (Phil. Acad. Sci. Swift coll.) ; 

 Galapagos? (Acad. Sci.). This specimen was mounted with F. 

 dnpctit-thouarsii, with which it was wrongly identified. The locality 

 given is typical for that species, but no F. distans has ever been 

 reported from it, or from any portion of the west American coast. 

 FUSUS CLOSTER Philippi. 

 (Plate III, figs. I and 8.) 



1850. Fusus closter Philippi, Abbildungen, vol. 3, p. 115, pi. 42 (Fusus, pi. s), fig. i. 

 1881. Fusus distans van closter, Tryon, Man., vol. 3, p. 58, pi. 36, fig. 132. 



The protoconch of this species is of the normal type, the earlier 

 portion smooth and erect, the last half volution with vertical ribs. 

 These are narrow, faint at first, but sharper later on, and from two to 

 tree times their width apart. There are seven or eight of these simple 

 ribs, including the final varix, with which the protoconch ends. The 

 riblets are very gently arched, with the convexity forward. 



The conch begins abruptly, with a round-ribbed and spirally striate 

 whorl. The ribs are generally strong, and closely crowded. In one 

 specimen (M. C. Z. 919) a smooth space, somewhat wider than a rib, 

 has been observed between the final varix of the protoconch and the 

 first rib of the conch. 



Three revolving spirals occur on the early conch, with an additional 



