458 NEW YORK STATE MUSEUM 



the sicula nor the number of types of thecae in one rhabdosome nor other 

 important characters have as yet been observed, it would be futile to 

 attempt a positive reference to one of the groups of the genus Mono- 

 graptus recognized in Europe. The thecae are those of a Monograptus 

 s. str. and resemble somewhat those of M . vomerinus Nicholson as 

 figured by Perner [1899, p. 18], from specimens preserved in relief. 



Freeh \loc. cit^\ has cited this form as a Rastrites. Although the 

 specimens when embedded in limestone, on account of the more or less 

 complete covering of the branches and the resulting prominence of the 

 horizontal denticles, resemble a Rastrites more than anything else, Girty's 

 type specimens which are entirely free, leave no doubt that the thecae are 

 not projecting as in Rastrites at right angles from a thin common canal, 

 but are normally overlapping as in true Monograpti. To bring out this 

 and several other features of the species not well shown in Girty's otherwise - 

 correct figures, I have redrawn several of the types in somewhat different 

 positions. The original of figure 436 [same as pi. 4, fig. 8 of Girty] shows 

 distinctly the thecal walls and what appear to be the apertures. The peri- 

 sarc of the denticles is broken off and the)' appear for this reason as very 

 blunt processes. Figure 437 [pi. 4, fig. 4 of original drawings] brings out 

 distinctly the acutely pointed form of the denticles, and figure 438 | pi. 4. 

 fig. 12, ibid.~\ which gives a somewhat oblique view shows the relatively 

 small apertures and the angular sides of the distal parts of the thecae. 



The " tabulae " which according to Girty's observations cross the coen- 

 sarcal canal at intervals, one for each serration [see pi. 4, fig. 3 of original 

 paper], and as stated in the explanation of plate 4, are seen in translucent 

 specimens, could not be found by the writer in those specimens which by 

 the loss of the perisarc have become translucent. They would represent 

 an interesting and novel feature whose existence, though asserted before 

 for certain graptolites [Hopkinson], has not been verified. Thin sections 

 exhibit, however, numerous cracks ol t he calcite filling which passing in 

 some pai'ts of the branches nearly straight transverse, are apt to produce 

 the impression ol tabulae |.wr hg. 430 1. 



