Fig. 77. — Changes in form of shell. A series of drawings illustrating the 

 changes from the early veliger (the first shell) , which is ^io of a millimeter in size, 

 to a 2-millimeter scallop. Note (a) change from flat-hinged veliger (1) to the pro- 

 dissoconoh (2), with prominent umbones; (6) return to a straight hinge (3), width 

 greater than height; (c) width and height become equal (8); (d) formation of 

 " ears" (10). 



