BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 439 



It may be mentioned in this connection that Hall has already 

 described and figured in the Palaeontology of New York, volume I, 

 as Orthoceras 1 a q u e a t u m an apical part of a conch with 

 strong longitudinal ridges or flutings ; the specimen, though found 

 loose in the drift, undoubtedly coming from the Beekmantown for- 

 mation, as we could convince ourselves on inspection of the same 

 which is deposited in the State Museum [3909 of the type 

 catalogue] from the character of the dolomite matrix. There are 

 hence two longitudinally fluted conchs known from the Beekman- 

 town formation, and both of these represent the apical parts of larger 

 conchs. Since it has been found that in later annulated forms 

 (as in O . b i 1 i n e a t u m from the Trenton by Clarke, O . 

 a n e 1 1 u s from the same formation by Ruedemann, and O . 

 c rota 1 urn from the Hamilton by Hall) a smooth or longitudi- 

 nally striated stage precedes the annulated stage of the conch, it is 

 proper to conclude that also the two small fluted conchs from the 

 Beekmantown represent the early stages of forms with annulated 

 conchs in the adult condition. We have also found last summer 

 such young fluted conchs belonging to annulated forms in the 

 Chazy formation. There apparently persisted from the Beekman- 

 town into the Hamilton a whole branch of annulated orthoceracones 

 and cyrtoceracones, all of which retained a fluted sculpture in the 

 apical portion of their conchs. The oldest, judging from Hall's 

 C . 1 a q u e a t u m , retained the longitudinal surface sculpture 

 longer than the latest, as O . crotalum. All of these facts 

 tend to demonstrate that the longitudinal sculpture in these forms 

 is in a retrocessional condition and that therefore, not as Hyatt 

 assumes the purely annulated forms precede in this family those 

 with both transverse and longitudinal markings, but that also phy- 

 logenetically. as in the ontogeny of the forms mentioned, a group of 

 forms with purely longitudinal sculpture preceded the annulated and 

 frilled forms, at least of this one branch of species. The inter- 

 esting ancestors with longitudinal sculpture only, would have to 

 be sought in the lower Beekmantown beds which thus far have not 

 furnished any fossils. In a long series of forms extending from the 

 Champlainic to the Carboniferous the longitudinal sculpture mark- 

 ings 'persist upon the annulations into the ephebic state. For these 

 the generic term Spyroceras has been proposed by Hyatt while in 

 others the annulations following upon the longitudinal ridges 

 disappear again before ephebic age is reached (Kionoceras). 



