22 Prof. W. King on Spirifer cuspidatiis. 



tlie use of the septum. The last of these points is of some 

 importance ; I may therefore be permitted to make a few 

 remarks on it in the present place. 



Although the canaliferous septum^ including that portion of 

 the dental plates which serves, as it were, for abutments, has 

 been compared with the arch-shaped chamber characteristic of 

 Cainarophoria^ PentameruSj and Stricklandmiaj I have some 

 grounds for disbelieving it to be the homologue of the latter 

 process. In Gamarojphoria and Strichlandiniaj guided by the 

 markings exhibited on some good casts of their chamber, and 

 the absence of anything similar on casts of the pertaining 

 valve, the muscles (their place in the genera mentioned is 

 occupied by ovarian scars) to which reference has been made 

 have undoubtedly been attached to the inner surface of the 

 process*; but as these muscles in Spirifer cuspidatus have 

 been fixed to the inner surface of the valve, the canaliferous 

 septum must have supported some others. Can it have 

 afforded attachment to the capsular muscle? In this case it 

 might be concluded that the canal itself lias served as a mus- 

 cular fulcrum for the dorsal pedicle-muscles^ which ordinarily 

 have one extremity implanted on the intercrural plate of the 

 dorsal valve, and the other attached to the pedicle f. 



Generic considerations. 



Although it has been shown that a number of Spirifers, in- 

 cluding the type, Sp. striatus^ are furnished with a canaliferous 

 septum, I do not on this account consider that 8p. cuspidatus 

 is a congeneric species ; for the apophysis in the former cannot 

 be said to exist beyond a comparatively rudimentary condi- 

 tion. Still I would not regard the more developed state of 

 the canaliferous septum to be sufficient to constitute a generic 

 distinction, were this appendage not associated with another 

 important character. A perforated shell-tissue has been found 

 in a number of species agreeing with Sp. cuspidatus in its 

 apophysary system : I am therefore led to consider that the 

 association individualizes a genus ; and hence I am also led 

 to adopt the name Syringothyris^ which Prof. Winchell has 

 appropriately applied to it. 



* It is the same with the saucer-shaped process of Leptc&na analoga, as 

 I showed in I80O. (See precited Monograph, p. 75, pi. 20. fig. 6.) 



t In Cyrtia exporrecta, which has no canaliferous septum, another 

 arrangement seems to have obtained. Judging from markings which I 

 perceive in the proper place on some good casts before me of this shell 

 from Connemara, apparently the dorsal pedicle-muscles were attached to 

 the dental plates adjoining the foramen. 



