BKYOZOA. 621 



The specimen represented by Meek's fig. 4a (loc. cit.), from 

 which his measurements were evidently derived, has much longer 

 pinnte than any yet seen by me, and I doubt very much that 

 it is the same species. It is attached to the matrix so that the 

 reverse side only could be seen. Figures 4c and 4d, represent- 

 ing the obverse side, agree with my own observations in all 

 respects excepting that the pinnae are too thin. Possibly a young 

 example was selected. In any event, it does not seem probable 

 that the Upper Coal Measures of Nebraska- contain two triline- 

 ate species. 



Position and locality: One of the most characteristic species 

 of the Upper Coal Measures. Examples are abundant at locali- 

 ties in Sangamon County, 111. The original specimens are from 

 Nebraska City, Nebraska. 



PTILOPORA McCoy, 1844. 



(Syn. Carboniferous Foss. Ireland, p. 200.) 

 (For generic diagnosis see page 398.) 



I have been in doubt whether this genus presented closer re- 

 lationship to the FENESTELLID.E or ACANTHOCL ADHERE. After 

 much thought I have concluded that the pinnate form of growth 

 must outweigh the dissepiments, the former being the result of 

 peculiarities in zooecial development, while the latter seem to 

 indicate nothing beyond an economical manner of giving solidity 

 and strength to the zoarium. It is true, of course, that in such 

 a species as P. paupera we see resemblance to some Fenestellids, 

 but on the other hand, P. valida and P. cylindracea, while pos- 

 sessing all the essential characters of Ptilopora, so closely re- 

 semble Pinnatopora. that a greater than generic separation is 

 out of the question. 



True species of the genus are first met with in the Hamilton 

 group, one is known from the Burlington limestone, three or 

 four from the Keokuk, and one, possibly two. from the Warsaw 

 and St. Louis beds. 



