GUAPTOLITES OF NEW YORK. I'AUT 1 739 



I) . r o t u n d a , D . t e n u i s t r i a t a and D . c a tn p a ii u 1 a t a . The first 

 three are cited from the Point Levis shales of Quebec, the fourth from the 

 Upper Llandeilo of the south of Scotland. The last species is very common 

 in the Trenton (Normanskill) graptolite slates of Nevy York and Canada and 

 will be noticed in the description of the Trenton graptolite fauna. Nicholson's 

 second and third species, which are also very common in the Deep kill slates, 

 are, without doubt, leached out shells of small undescribed brachiopods, 

 referable to Acrotreta and Paterula. The first species, D. acuminata, 

 which is the genotype, is represented by long, oval, corneous bodies, which 

 have one extremity prolonged into a long acuminate mucro. The genus, 

 originally proposed for an agglomeration of variously shaped bodies, belong- 

 ing to entirely different groups, should evidently be restricted to fossils of 

 similar form and character. 



Nicholson's contention that these fossils were gonangia of graptolites has 

 never found any recognition, and this for good reason ; for, while they are 

 found associated in great numbers with the graptolites and only with these, 

 they have never been observed in direct attachment to any part of the rhabdo. 

 some, but are always found entirely free. Their mere association with the 

 graptolites is no evidence of their being a part of the graptolite structure ; 

 just as little the minute brachiopod shells,^ mostly of oboloid type and found 

 often in immense numbers associated with graptolites, would be considered as 

 parts of graptolites. 



As these fossils have not been considered to be of graptolitic nature, we 

 do not find them cited in the lists of graptolites, as for instance in those of the 

 Skiddaw or of the St David's shales. Lapworth mentions D . c a m - 

 panulata in his Catalogue of the Western Scottish Fossils [p.7] ; but 

 among the crustaceans. Ami [1889, p.ll7k] cites three forms of Dawsonia with 



' The brachiopods of the graptolite shales are, from the Cambric shales to the Utiea 

 epoch, so similar in all their characters that, while belonging to different genera, they 

 probably furnish an excellent instance of adaptation to a definite mode of life — per- 

 haps a pseudoplanktonic existence by adhesion to floating seaweeds. They will, at an 

 opportune time, be made the subject of a separate investigation by the writer. 



