554 GEORGE H. GIRTY 



false premise, on an unsupported assumption, and on loose reason- 

 ing, and that it cannot stand. 



If, as remarked by Professor Schuchert, several different types of 

 Spirifer exhibit a tendency to develop the split tube, and if the 

 development of this structure may be looked for in almost any high 

 areaed member of the genus, far from adopting the course which 

 he advocates of establishing a new genus for every such manifes- 

 tation, I should feel that this series of facts materially lessened, if 

 it did not destroy, the value of the syrinx as a generic character. 



The function of the syrinx is not definitely known. The most 

 probable explanation of its function, and the one adopted by Pro- 

 fessor Schuchert, is that it is connected with the pedicle muscle. 

 Even in typical Syringothyris there is no cogent reason for inferring 

 that the soft parts possessed any structures different from those 

 of Spirifer. If so, this typical structure of Syringothyris is prob- 

 ably to be regarded only as a result of excessive shell secretion, and 

 it may well be questioned whether its employment as a generic 

 character is any more justifiable than it would be so to employ 

 the deposit of an apical callosity, with which the syrinx is perhaps 

 a concurrent manifestation, or of a thick test with attendant deep 

 muscular imprintation, a character regarded of little importance 

 in other types of brachiopods. The tendency to develop an 

 incipient syrinx in various groups of Spirifer contributes not a 

 little to justify such a low estimate of the taxonomic value of this 

 character. 



