THE GENUS SYRINGOPLEURA SCHUCHERT 551 



Professor Schuchert says that the erection of a genus is demanded 

 by the fact that S. randalli has a different phyletic derivation from 

 typical Syringothyris. 1 He is unfortunately not very explicit but 

 he apparently derives typical Syringothyris from the ostiolate 

 Spirifers and 5. randalli (Syringopleura) from the aperturati. 

 But it is a fair hypothesis that 5. randalli, the hypothetized ran- 

 dalli, may have come from typical Syringothyris by the introduc- 

 tion of mesial plications at so early a period that in the imperfect 

 condition of our record the two types seem to have developed nearly 

 simultaneously. Or, a second hypothesis is not negligible, that 

 the two may have sprung from some common ancestor, at present 

 unknown, which was intermediate between the ostiolate Spirifers 

 on the one hand (or whatever stock gave rise to Syringothyris) 

 and Syringothyris and "Syringopleura" on the other. Professor 

 Schuchert offers no evidence to support his theory of the deriva- 

 tion of 5. randalli as against these two other possible hypotheses. 2 



But even if we grant that there is a species with the characters 

 of S. randalli and that it is derived from some other group of 

 Spirifers than that which gave rise to typical Syringothyris, a 

 scrutiny into the line of reasoning which justifies the erection of a 

 new genus from these premises will not, I believe, be without profit. 

 The argument seems to be that, because 5. randalli and typical 

 Syringothyris belong to different phyla, therefore it is necessary 

 to place them in different genera. 



Originally and strictly the word phylum in biology is used 

 for one of the larger divisions of the animal or vegetable kingdom, 

 but it seems to be often employed for small groups standing in a 

 line of genetic relationship. Thus phylum has a variety of mean- 

 ings as regards comprehensiveness. We might even say that two 

 Spirifers belonging to the same species but having different lines 

 of descent for numerous generations belong to different phyla; 



1 Professor Schuchert is perhaps a little misleading in his expression which seems 

 to limit Syringothyris to what he calls the Mississippian sea. Characteristic Syrin- 

 gothyris, of course, occurs not only associated with "S. randalli" near Warren, but 

 at other localities and horizons in the same province. 



2 Still other hypotheses are possible, equally plausible with these. For instance, 

 Hall and Clarke name a number of ostiolate Spirifers with incipient plications on the 

 fold and sinus. 



