CJUAPTOLITES OF NEW YOUK. TAUT 1 729 



dentiitus. The same author cites it in his list from Arkansas. Hop- 

 kinson aud Lapworth identified a small, more obtusely pointed form, ^vhich 

 they obtained fi'om the Louver Arenig of Eamsey island in Wales, ^vith 

 this species. The latter, if not identical, represents a closely related smaller 

 type. Typical specimens were collected and desciibed b}' H. A. Nicholson 

 from the Upper Skiddaw slates (Ellergill beds) which are homotaxial with 

 the beds with D i p 1 o g r a p t u s d e n t a t u s in the Point Levis and Deep 

 kill regions. Miss Elles also had typical material from the same horizon of 

 the Skiddaw slates for investigation. 



Heniarlcs. This species was doubtfully referred by its author to 

 Retiolites. When Nicholson erected the genus Trigonograptus, he assigned 

 R e t i o 1 i t e s e n s i f o r m i s to it, though the genotype was described 

 as having a zigzag virgula, and this form has a straight one. 



It appears that neither in Canada nor in England specimens of such 

 gigantic size were observed as the fragments in the Deep kill beds must 

 have come from. Hall's largest specimen measured nearly 24- in. (about 

 62 mm), while Miss Elles had a fragment measuring 38 mni. The one i-epro- 

 duced here in fio-iire 3 measures 80 mm. 



o 



Family cLiiviAcoGFeAPTiDAE Freeh 



CLIMACOGRAPTUS Hall. 1865 



This genus, which becomes so prominent, both in number of species 

 and individuals, in the higher zones of the Lower Siluric, is repre- 

 sented by but two species, one of which, C . p u n g e n s , though an 

 undoubted Climacograptus, is a very diminutive form, ^vhile the other, 

 C . ? an teun a r i u s, can be referred only with doubt to climacograptus. 



On account of this meager representation of the genus in the lower 

 Lower Siluric, we reserve the discussion of its chai-acters foj* the next memoir, 

 in which we shall be better enabled to illustrate them with the aid of the 

 larger and moi-e typical Trenton material. 



