PHYLOGENY OF FUSUS AND ITS ALLIES. 1 5 



interspiral space on the under side of the whorl, which is generally 

 free from spirals. 



FUSUS ACUMINATUS Sowerby. 

 (Plate I, figs, I, 2.) 

 1/66. Murex porrectus Solander (pars.), Foss. Hants., fig. 2)^. 

 1821. Fusus acuminatus Sowerby, Min. Conch., vol. IV, p. 131, pi. 274. 

 1821. Fusus aciculatus Sowerby, Min. Conch., vol. IV, corrigenda. 



This name deserves to be revived for the species originally de- 

 scribed under it by Sowerby. His description on page 131 of his 

 Mineral Conchology fits well the specimens here figured and described 

 under this name. Solander's Altirex porrectus, fig. 36, in Brander's 

 Fossilia Hantsoniensis which is cited by Sowerby as an example of 

 this species, is a good illustration. In the corrigenda to volume IV 

 of the Mineral Conchology F. aciuninatiis is made a synonym of F. 

 aciculatus and as such it has since been generally regarded. Deshayes 

 figures a Parisian specimen as a typical F. aciculatus, a form very dif- 

 ferent from that described by Sowerby and figured by Solander. 

 Sowerby's species represents what appears to be a phylogerontic type, 

 while the typical F. aciculatus is a progressive type, both, however, 

 tracing their ancestry to the British F . porrectus. 



The only specimen preserving anv trace of the protoconch, in the 

 collections examined, was imperfect ; but the last portion remains 

 (fig. 2), showing all the features found in the preceding species. The 

 termination is abrupt, and the nepionic shell 

 begins as abruptly. The spirals, seven of 

 which appear on the nepionic whorl, are 

 strong, sharp and separated by wide inter- 

 spaces. They appear particularly marked on 

 account of the faint development of the ribs. 

 These are nearly obsolete, occurring mainly 

 as faint wrinkles or wavings on the whorls, Fig- 2. Fusus acumi- 



though on some of the neanic whorls they "f f • ^he protoconch 

 ^ , , . -^ of fig. 2, pi. I. The to- 



arc moderately promment. ♦.,! i . c u .1 



^ - ^ tal absence of ribs on the 



The whorls of the conch are uniformly shell is only apparent and 



rounded, and rather loosely joined, leaving a due to the position in 



deeplv impressed suture. This feature is which the specimen was 



characteristic of the primitive F. porrectus. drawn ,-. e to the direc- 



HM . ... 1- , . , tion of the light. (M. 



i here is even an mcipient canaliculation along q -^ ^ 



the suture, which in some cases does not pro- 

 ceed beyond a flattening which can be traced backward to a number 

 of whorls, becoming gradually obsolete. This flattening does not 

 occur in the young. 



This species is either primitive or phylogerontic. The loose coil- 

 ing and simple spirals (without intercalations) indicate the former 



