GRAPTOLITES OF NHW VORK. TART 2 



23 



Dicellograptus divaricatus {Hall) Cryptograptus tricornis (Carruthers) 



D. intortus Lapworth Climacograptus bicornis Hall 



Dicranograptus ramosus Hall C. antiquus Lapworth ? 



I), nicholsoni var. parvangulus Gurley Glossograptus whitfieldi (Hall) 

 CorynoideS gracilis mitt, perungulatus ' G. ciliatus Emmons 



nov. Lasiograptus mucronatus ( Hall) 



Diplograptus foliaceus Murchison Leptobolus walcotti" Ruedemann 

 D. angustifolius Hall 



This association leaves no doubt of the homotaxy of the beds with the 

 Dicellograptus zone of New York. But the black Arkansas shales also 

 contain a few forms which by number and relative size are very prominent 

 in the faunule and which do not occur in the Appalachian valley trough. 

 These are : 



Dicellograptus divaricatus var. rigidus Dicranograptus nicholsoni var. arkansas- 

 Lapworth ensis Gurley 



Diplograptus foliaceus var. trifidus Gurley 3 

 The most noteworthy feature of these three forms is that the)' are 

 identical with British varieties while they have not yet been observed in 

 either eastern America or Australia. Dicellograptus divaricatus 

 var. rigidus is a Glenkiln form, first described by Lapworth. Dicr. 

 nicholsoni var. arkansasensis is, as noted in the description of 

 the form here given, quite probably identical with an undescribed British 

 variety of Dicr. nicholsoni that is figured in the Monograph of British 

 Graptolitcs, plate 25, figure ig, though the Normanskill shale of New York 

 has also furnished a similar form in D . s p i n i f e r var. geniculatus. 



'Overlooked in the original listing of the Arkansas graptolites. 



2 Not listed by Gurley, but since described by the writer from the Normanskill shale 

 of New York. 



3Dr Gurley lists also from Arkansas: D i c ty on e m a obovatu m n. sp.-, L e p t o- 

 g r ap t u s cf. an n e c t a n s and Dicellograptus elegans var. The first of these, 

 based on a single type, I have been unable to find in the collection of the National Museum 

 from Arkansas; the second identification refers- to a very poorly preserved specimen and 

 the third again has not been found. The last named species in England pertains to a 

 higher horizon and its identification is doubtful [see Gurley 1896, p. 296]. 



