568 PROCEEDINGS OF THE ACADEMY OF [Oct., 



In spite of their shortcomings it is beheved that diagrams give a 

 closer approximation to the truth than verbal descriptions and can 

 be employed to greater advantage if their limitations are understood. 



Though fully appreciating the necessity for the correct use of 

 systematic terms, the author wishes to emphasize the point that the 

 present study has not for its object the comparison of species as 

 ordinarily understood, but the comparison and correlation of the 

 morphologic combinations exhibited by the majority of individuals 

 of communities or races. 



Wherever practicable, the forms examined have been compared 

 with type specimens. When this could not l)e done satisfactorily 

 it has been the policy to refer, if possible, to some good figure of a 

 specimen whose horizon and locality are known. Though this latter 

 method may perhaps increase the chances of confusion among names, 

 it is believed that it lessens the chances of confusing morphologic 

 units. 



In the group of gastropods under discussion the shell characters 

 most available for comparison are the sutural canal, the nodes on 

 the shoulder angle, and the shoulder-angle keel. The appearance 

 and disappearance, strength or weakness, persistence or the reverse 

 of these characters have been used in comparing one race or species 

 with another. Decortication in many fossils and mechanical abrasion 

 in most recent specimens have usually obscured the minute details 

 of the first and second whorls. It is therefore not possil)le to compare 

 here every ontogenetic stage, but it can be stated that the sequence 

 of ontogenetic stages for the group appears to be (1) a smooth and 

 rounded stage, (2) a short cancellated and rounded stage, (3) an 

 angulated and noded stage, (4) an angulated and keeled stage without 

 nodes, and (5) a final rounded stage in which only the faintest spiral 

 striae remain. 



In the present study, as mentioned above, the last three stages 

 are, together with the canal, the most useful for comparative purposes. 

 It is unfortunate that it is not practical^le to extend the comparisons 

 in detail to the first and second whorls, but the nodes are usually 

 much obscured on the second whorl, while the cancellated stage is 

 known to the author in only one fossil race. Its presence, though 

 not proved, is suspected nevertheless for the entire group of canalicu- 

 late Fulgurs. 



In order to restrict, as far as possibl(>, tlu^ verbal description of 

 each feature in each whorl of each race, it is deemed advisable to 

 present the diagrams first and allow them to s(n-ve as a guide to the 



