3/8 NEW YORK STATE MUSEUM 



might say that it has still the outside appearance of a diplograptid, but the 

 inner structure of a retiolitid. But the difference is quite probably only one 

 of grade of reduction of the outer layer of the periderm and the latter may 

 have persisted as a thin membrane also in Retiolites and Gothograptus. At 

 least this is suggested by Wiman's statement [ibid. p.41] that in Gotho- 

 graptus nassa small lappets are observed which ma}' be the remains 

 of a membrane that filled the meshes. Glossograptus quadrimu- 

 cronatus probably represents a stage with still stronger outer layer and 

 less developed retioloid second layer. 



The genotype is G . c i 1 i a t u s Emmons. This contains, as has been 

 mentioned above, Grapt. spinosus Hall as a synonym. There is no 

 doubt in my mind, that G. setaceus Emmons, a form of which neither 

 locality nor formation is given and which is insufficiently described from a 

 fragment, that was "evidently injured" should be considered as another 

 synonym [see text fig. 325]. 



Diplograptus ciliatus Emmons from Augusta count)', Virginia, 

 is clearly also a Glossograptus. Gurley has in recognition of this fact, 

 and since the name G. ciliatus is preoccupied, proposed the name G. 

 a r t h r a c a n t h u s for the species [1896, p. 78]. The peculiarities of this 

 species are seen in the spines which according to Emmons are " bulbous, 

 and jointed or transversely marked " and in the character of the " denticles," 

 of which Emmons states, "serrations unequal, the intervening smaller serra- 

 tions rounded, the larger prolonged and run into the base of the ciliae " 

 [see text fig. 327]. The latter duplication of the denticles has been 

 explained by Gurley, as being probably due to "a slightly oblique pressure 

 causing the lower lateroventral margin of the polypary to extend beyond 

 the upper lateroventral margin of the same, in such a manner that the 

 corners of the thecal mouths alternate." Likewise are the bulbous anil 

 jointed character of the spines, from which Gurley has derived the new- 

 name for the species, in all likelihood due to the preservation ol the speci- 

 men. 1 have observed like bulbous ends of spines in G. ciliatus [see 

 pi. 26, fig. 8] and in other spinose graptolites and consider them as caused by 



