254 S. W. Ford and W. B. Dwight — Fossils obtained 



to make any sure assignment of tbem. Fig. 13 is quite possi- 

 bly a partial transverse section of a shell belonging to the 

 group above referred to Pleurotomaria suhtilislriala but is not 

 sufficiently definite to enable us to decide this point. Forms 

 14 and 15 we have simply figured as they appear in polished 

 sections, but prefer for the present, to make no definite disposi- 

 tion of them. They seem to be either distorted forms, or acci- 

 dental combinations of independent structures. 



Crustacea. — The single fragment of the free cheek of a 

 trilobite shown in fig. 16, is the only fossil of this class thus far 

 obtained from the Canaan limestones. We think that it may 

 represent the genal spine of some such species as Asaphus 

 megistos. 



Fig. 17 apparently represents a coral, which we think, is 

 likely to be the Ghceleles lycoperdon. It is a portion of a trans- 

 parent rock section taken from limestone collected by Professor 

 Dana upon Hall's farm above mentioned. We have been led 

 to suspect the presence of corals, very much altered, among the 

 organisms from the other localities; but have found nothing as 

 definitely outlined as the specimen figured, that can be safely 

 regarded as of this nature. In several of the slices we have 

 also detected what appears to us to be a Stromatoporoid form. 



Concluding Remarks. 

 Judo-ins: from the facts above presented, we strongly incline 

 to the opinion that the limestones of Canaan, N. Y., which 

 have afforded the fossils in question, are of Trenton age. We 

 are unable to assert positively that the three Trenton species 

 Cleiocrinus magnificus, Pleurotomaria subtilistriata, and Murchi- 

 sonia gracilis have been identified among the organisms ob- 

 tained from these limestones; but we neverthless feel very 

 confident that the forms which we have recognized as probably 

 such, will turn out to be what we have considered them. We 

 consider it safe to affirm that one species, the Murchisonia gra- 

 cilis, has been recognized with so much probability, that its 

 identification may be regarded as established with as much 

 certaintv as is possible from a study of sections alone ; and we 

 feel almost equally confident in regard to the Pleurotomaria 

 subtilistriaia. It should be remembered that the more decisive 

 forms brought to our notice, have been presented to us, with 

 but few exceptions, either in polished surfaces or transparent 

 rock-sections ; and that the difficulties in the way of correct 

 determination have been, in consequence of this, greatly in- 

 creased, as compared with determinations undertaken in the 

 usual manner. We present this brief paper hoping that it may 

 serve to throw additional light upon a much debated region, 

 and lead to the development of still more convincing paleonto- 

 logical testimony concerning the precise age of its strata. 



