1914.] NATURAL SCIENCES OF PHILADELPHIA. SGO' 



explanations that may follow. The purpose of th(^ diagram is to 

 picture the persistence or the reverse of the different characters in 

 passing from the early to the late whorls, that is, throughout the 

 ontogeny of the average individual' of a race. 1'he heavy horizontal 

 line of the diagram represents the ontogeny. Tt might be described 

 as a linear representation of that which in the shell is spiral: — the 

 spiral shell unwound, if we may use such an expression. Above 

 this line the ontogenetic stages are marked off as follows: 



A. The smooth antl rounded stage.^ 



X. The noded stage. 



K. The keeled stage without well defined nodes. 



R. The final rounded stage. 



The ontogenetic range of the sutural canal is shown below the 

 heavy line mentioned. The vertical dotted lines delimit the different 

 whorls and the spaces between them are numbered accordingly. 



It has been found by measurement that (due to ventricose coiling) 

 the length of the shoulder on any one whorl is about twice as great 

 as that on the preceding whorl. This, though not mathematically 

 correct, is believed to be so close an approximation to the truth that 

 the diagrams can be constructed in this manner. Whorl seven is 

 accordingly shown as twice as long as whorl six, and this proportion 

 is maintained down to the third whorl. (See tables on p. 570.) 



The Coronatum-pyrum Sequence. 



The sutural canal or channel which is such a prominent character 

 in our two Recent species of canaliculate Fulgurs and which is 

 usually selected as the chief diagnostic feature of the genus or sub- 

 genus Sycotypus had its beginnings at least as early as the Ballast 

 Point Oligocene. It is here, as pointed out by Dall', more of an 

 individual than a racial or specific character, but it is none the less 

 present, and in any account of the canaliculate Fulgurs one must 

 not fail to mention those Florida specimens which are provided with 

 the shell structure in question. They are usually assigned (see 

 A. X. S. P., Xo. 10,514) to Fulgnr spimger (Conrad), but their rather 

 wide divergence from the type of that species is made evident by a com- 



1 It cannot be too strongly emphasized that the tabulated results are intended 

 to apply only to those specimens which are regarded as average. In every race 

 or species individuals may be selected which exhibit either more or less accelera- 

 tion of shell characters than does the average example. 



- In the diagrams the cancellated stage when known to be present is included 

 with stage A. 



3 Trans. Wagner Free Indilnle of Science of Phila., vol. Ill, pt. 1. p. 111. 



