PTEROPODA. 177 



Devonian fauna. 



"Styl. striata, . . Richter, . . Cypridinia schists,' 

 St. lubrica, . . Ludwig, . . ^ 

 St. intermissa, . " • • r Kramenzelstein, . 



St. crenato- striata, " . . J 



St. bicanaliculata, " . . Eifel, 



St. laevigata, . . F.A.Rcemer, Harz, .... 



St. laevigata, . " « I. 



III. 

 II. 



" The majority of the known forms of this type being found in the forma- 

 tions which crown the Devonian system, we may be surprised at their sudden 

 and total disappearance before the end of these deposits. No form of the 

 genus Styliola has hitherto been observed in the Carboniferous system, which 

 also contains no trace of Tentaculites. These two genera seem then to disap- 

 pear at the same time, which renders their reciprocal relations more marked." 



One species at present known to us in America has a comparatively extended 

 geological range. The^ S. Jissurella begins its existence in the Marcellus shale, 

 occurs also in the shales of the Hamilton group above, and in the Genesee 

 slate, disappearing in the Olive shales above the base of the Portage group. 

 In the Marcellus shale, and lower part of the Hamilton group, this species is 

 associated with Tentaculites gracilistriatus, but the latter form is at present 

 unknown in the centre of the Hamilton group or in any higher position ; the 

 Styliola alone, so far as known, being present in the superior strata. 



In its geographical distribution, the S. Jissurella has a remarkable range, 

 being known throughout the entire extent of the State of New York from east 

 to west — a distance of more than thre,e hundred miles. It also occurs in the 

 western extension of the Genesee slate and associated rocks, in the State of 

 Indiana, where the New Albany black shale, at Lexington, presents large 

 surfaces quite covered with Styliola. It has, therefore, a geographical exten- 

 sion of more than seven hundred miles in a direct line from its most easterly 

 known locality. There is little doubt but it will be found also in Ohio and in 

 Canada West (Ontario). 



In some of its phases it does not seem possible to separate this species from 



Htyliola clavulus, of Barrande, by any external or internal characters thus far 



described or illustrated. The fossils are minute, smooth or striated acicular 



tubes, presenting in all respects similar features, and having similar associa- 



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