132 WEST COAST SHELLS 



Bathytoma tryoniana^ Gabb, Tryon's Turret-shell, 

 resembles the last S])ecies, but the whorls are con- 

 vex, angular, and ornamented by a row of nodes on 

 the angle. It has been hauled up alive in the fisher- 

 men's nets at San Pedro. 



There are several fossil forms in Oregon and Cali- 

 fornia which greatly resemble the last three species, 

 and which seem to indicate that they were all closely 

 related through their ancient ancestors. Various 

 names have been given to these old forms, such as 

 Bathytoma gabbiana, Dall, to a fossil shell found 

 near Coos Bay, and Bathytoma keepi, Arnold, to a 

 form found near Coalinga, which may have been an 

 ancestor to the recent Bathyto??ia tryoniana. The 

 study of fossil shells has been an important means of 

 increasing our knowledge concerning the original 

 forms of living shells, and sometimes old and cher- 

 ished names have had to be changed on account of 

 this knowledge. This is often troublesome, no 

 doubt, but we may be consoled by the thought that 

 these changes, sometimes at least, mean that the sci- 

 ence of Chonchology is alive and not dead. 



Figure 102 gives us a magnified view oi the shell 

 of T//rm perversa^ the Perverse Turret-shell. It is 

 called perverse because the whorls revolve from left 

 to right, instead of in the usual way. It is called 

 liurns^ instead of Fteiirotoma^ meaning Notch-side, 

 as it is called in the old edition, because it is found 

 that T^urris is the older name. In regard to this 

 change of names Dr. Dall remarks, "It is always 

 regrettable to part with an old and familiar name, 

 but in the present case, if the rules of nomenclature 



