578 PROCEEDINGS OF THE ACADEMY OF [Oct., 



and exaggeration serve as a basis for the species of systeniatists. 

 It has no higher classificatory value. 



The Final Rounded Stage: 



(a) Late Miocene to Recent in this group. 



(6) An ascendant character appearing only in the most specialized 

 species {F. pynun, F. incile). Never a declining character, though it 

 may perhaps be indicative of decadence.- 



(c) Never appearing in primitive forms. Appearing early in the 

 sixth whorl of the most specialized form {F. pyrum Caloosahatchie 

 Phocene). Never, in this group, followed by any other ontogenetic 

 stage. 



(e) Its chief changes are due to its degree of exaggeration. 



(/) Its changes through exaggeration help to serve as a basis for 

 the species of systematists. It has no higher classificatory value. 



In the preparation of these notes the collections most extensively 

 studied were those of The Academy of Natural Sciences of Philadel- 

 phia and of the Wagner Free Institute of Science of Philadelphia. 

 Acknowledgments are due to the officers of these institutions for 

 many courtesies and to Mrs. Ethel Ostrander Smith for the careful 

 execution of the drawings. 



Explanation of Plate XXIV. 



Fig. 1. — Fulgur coronaium Conrad. Miocene (St. Mary's). St. Mary's River, 

 Md. Apical view of an adult individual of about 6| whorls. Illustrates 

 a rather primitive type of the sutural canal and a vigorous noded stage 

 which persists to the end of the ontogeny. Diameter of last whorl at shoulder 

 = 79 mm. 



Fig. la. — Side view of specimen shown in fig. 1. 



Fig. 2. — Fulgur rugosum Conrad. Miocene (St. Mary's). St. Mary's River, 

 Md. Apical view of an adult individual of about 7 whorls. Shows a well- 

 developed sutural canal and a degenerating noded stage with its gradual 

 transition into a keeled stage toward the end of the seventh whorl. Diameter 

 of last whorl at shoulder = 100 mm. 



Fig. 2a. — Side view of specimen shown in fig. 2. 



Fig. 3. — Fulgur canaliculatum (L.). Recent. Apical view of an immature indi- 

 vidual of about Gf whorls. Shows a well-developed sutiu'al canal and an 

 accelerated and degenerate noded stage, which passes into a keeled stage 

 toward the end of the sixth whorl. Diameter of last whorl at shoulder = 

 67 mm. 



Fig. 3a. — Side view of specimen shown in fig. 3. 



Fig. 4. — Fulgur incile Conrad. Late Miocene. Yellow marl of Burwell Bay, 

 James River, Va. Apical view of nearly mature individual of 6j whorls. 

 Shows a highly developed sutural canal, a much ticcelerated and com- 

 pressed noded stage, and an accelerated and compressed keeled stase which 

 passes into a final rounded stage toward the end of the si.xth whorl. Diameter 

 of last whorl = 81 mm. 



Fig. 4a. — Side view of specimen shown in fig. 4. 



