■^ 



Fhe Nautilus. 



Vol. XXV. FEBRUARY, 1912. No. 10 



NOTES ON THE VARIATION OF STROMBUS PUGILIS. 



BY CHARLES W. JOHNSON. 



A large series of Stromhus pugilis Linne, with its varieties alattis 

 Gmel. and nicaraguensis Fluck, together with its Pacific analogue, 

 S. gracilior Sowb., and their Oligocene precursors, S. proximus 

 Sowb. and S. pugiloides Guppy, form a very interesting group for 

 studying the evolution and variation of a species. 



Young specimens (lacking the body whorl) differ even more in 

 general appearance than the adults. The apices of most specimens 

 are usually wanting, but a young example of the typical form and 

 one of the variety alatus, in the collection of the Boston Society of 

 Natural History, show the following differences : In pugilis the Jirst 

 two whorls are entirely smooth ; the third with obsolete longitudinal 

 ribs ; the fourth, fifth and sixth with prominent ribs and two or three 

 varices to each whorl, but without spiral lines ; seventh with ribs, 

 spirals and varices; eighth nodulose, with a varix and prominent 

 spirals ; ninth nodulose, with prominent spirals ; tenth with coarse 

 spirals and fine intermediate lines ; the row of nodules are almost 

 covered by the following whorl ; the eleventh (preceding the body 

 whorl) has long spines at the periphery, a few spirals below the suture 

 and at the anterior half, the remainder of the whorl being smooth ; 

 length of specimen 42 mm. 



In the specimen of alatus the protoconch is l)roken, but a part of the 

 third whorl would indicate two smooth whorls, as in pugilis; the 



