452 NEW YORK STATE MUSEUM 



reversed in direction opposite the aperture of the sicula. Early thecae 

 adhering for two thirds of their length to the common canal, projecting 

 horizontally with their last third and bending slightly in sicular direction 

 with their apertural portion ; numbering 11 to 12 in 10 mm; their apertures 

 furnished with a short, stout, horizontal apertural mucro ; those of the adult 

 parts overlapping two thirds of their length, inclined at an angle of 30 , 

 numbering 9 to 10 in 10 mm ; their free, apertural portion sharply recurved 

 so as to become parallel to the axis of the rhabdosome and contracted 

 towards the aperture ; the latter horizontal, occupying but one fifth the 

 width of the rhabdosome. Synrhabdosomes and a nemacaulus have not 

 been observed. 



Position and localities. Hall in his original description has recorded 

 this species "as very abundant in the upper green shale" of the Clinton 

 group at Soclus, Wayne co., and also as occurring in the eastern part of 

 Williamson and in the banks of the Genesee river at Rochester. Other 

 localities of the Clinton belt, where the upper shales are exposed, as 

 Palmer's Glen near Rochester, have also furnished this graptolite in abund- 

 ance. In the course of the investigation of the stratigraphy of the Clinton 

 group, now in progress, the exact horizon of this and other Clinton 

 graptolites will be determined. 



Remarks. The similarity between M. priodon and M. c 1 i n t o n- 

 e n s i s is so o-reat that several authors inclined to make the latter a 

 synonym of the former; e. g. Linnarsson [1879] who however remarked 

 that in our present state of knowledge they are most conveniently regarded 

 as distinct. Lapworth, on the other hand [1880] states that he is sure 

 that their individual distinctness will eventually be placed beyond question. 

 Freeh \foc. eit.~\, again, has considered our form as a mere mutation of prio- 

 don, from which it is said to differ by the tubular prolongation and straight 

 truncation of the thecae, and also Dr Gurley has stated in a manuscript 

 note "that its resemblance to L. priodon is so close as practically to 

 amount to identity." The: general similarity between the two tonus is 

 indeed considerable, still there are important differences ; those already 



