Oh the Montiadiporoids of the Cincinnati Group. 141 



In order to show the difficiihies to be encountered in identify- 

 ing some of these genera of Mr. Ulrich's, a few quotations will be 

 given. First in reference to Eridopora, Ul., he says, after giving 

 the description : "As may be gathered from the above descrip- 

 tion, the genus is exactly intermediate between CeramoporcUa, Ul- 

 rich, and FistuHpora, McCoy. Externally its species resemble the 

 former, while their external (!) [internal?] characters simulate very 

 closely those of certain species of the latter genus."* Again in 

 speaking of one of his new species, Ainplexopora robusta, he says : 

 "Care must be taken in separating the species from MonotnpcUa 

 cequalis, UK, which the smaller specimens of A. robusta strongly 

 resemble." t Again, as showing the estimate placed upon certain 

 well known variable features, and as illustrating Mr. Ulrich's idea 

 of what is a good generic or specific character, we read. "I have 

 studied two species which differ from the typical forms of the genus 

 in one character, namely, in possessing a limited number of smaller 

 cells than the average, which appear to be of the nature of intersti- 

 tial cells. The next described species, M. \onotrypdla\ sub quadrata, 

 is one of these. This species, in all other respects, resembles M. 

 qiiadrata, so nearly that I am forced to regard them at least as be- 

 longing to the same genus. The other species, though quite dis- 

 tinct, is yet so near to M. \onotrypeUa\ cequalis, that despite the 

 interstitial tubes, I cannot regard it as belonging to another genus. "+ 

 [to be continued.] 



*Ibid V. 137. 

 f'bid vi.'s^. 

 |lhid V. 248, 249. 



