1914.] NATURAL SCIENCES OF PHILADELPHIA. 571 



parison with the figure which accompanies the original description.^ 

 They are without doubt a very primitive expression of the canalicu- 

 late type, but entire individuals of the series are all of small size, and 

 the suspicion that they are not fully grown has prevented the author 

 from including them in the tables with mature examples of other 

 specie^. It is therefore considered better to begin the discussion of 

 morphologic sequences with a later though perhaps equally primitive 

 form — Fulgur coronatura Conrad^ — from the St. Mary's Miocene, 



The most striking sequence starting with this species terminates 

 with a form from the Caloosahatchie Pliocene of Florida, which is 

 usually included in Fulgur pyrum. (Dillwyn). The steps in the 

 sequence are F. coronatum Conrad (St. Mary's Miocene), F. rugosum 

 Conrad^ (St. Mary's Miocene), F. canaliculalum (L.)^ (Maryland 

 Pleistocene), F. pyrum (Dillwyn)^ (Recent Florida), and F. pyrum 

 (Dillwyn) (Florida Pliocene). These are all shown in Table I. 

 Pleistocene specimens of F. canaliculatuni have been selected because 

 their preservation is superior to that of the available Recent speci- 

 mens. It should also be noted that the ontogeny line which has 

 been introduced for the Recent F. pyrum cannot be used to represent 

 all individuals of the species.^ 



On consulting the table it will be seen that the sequence consists 

 (1) in the progressively earher appearance of the canal in passing 

 from F. coronatum to the Caloosahatchie F. pyrum, (2) the progress- 

 ive shortening of the noded stage through compression of the stage 

 and acceleration of its later part, (3) the introduction and progressive 

 acceleration of the keeled stage and its final compression in the 

 terminal member of the sequence, and (4) the introduction of a final 

 rounded stage in the Caloosahatchie F. pyrum^° accompanied by 

 compression and acceleration of the noded and keeled stages. 

 . However little this arrangement may conform to geologic order 

 or to one's ideas of phylogenetic relationship, it must be admitted that 



^J. Acad. Nat. Sci. Phila., vol. 1, 2d ser., p. 117, pi. XI, fig. 32, 1848. 



* "Fossils of the Medial Tertiary," pi. XLVI, fig. 1. 



See also Md. Geol. Surv., Miocene, pi. XLYI, figs, la, lb. 



6 "Fossils of the Medial Tertiary," pi. XLVI, fig. 4. 



See also Md. Geol. Surv., Miocene, pi. XLVI, figs. 2a, 2b. 



• See Md. Geol. Surv., Pliocene and Pleistocene, pis. XLVI, XLVII, XLVIII. 

 8 "A Descriptive Catalogue of Recent Shells," L. W. Dillwyn, London, 1817, 



p. 48.5. 



Martini Lister Syn. Method. Conch., 3d ed., 877, 1. 



See also Mnnval of Conchology, G. W. Tryon, 1 ser., vol. Ill, pi. 58, figs. 402, 403. 



^_ The suspicion is entertained that the Recent F. pyrum will eventually prove 

 divisible into two species or at least races. 



1" This stage is also seen in many specimens of the Recent F. pynim. 

 38 



