0)1 the Feyiestellidce — Irish Carboniferous Strata. 103 



one hope that further research may show that some of its 

 relatives also reached the Carboniferous period ; and the 

 number of Fenestellids recorded by Sir R. Griffith' from the 

 base of the Irish Carboniferous strata points to the shaly beds 

 of the south as a possible field of observation. But Hemitrypa 

 seems the natural survivor of the series that leads on up to it 

 from Semico scinium, and this genus is fortunately already well 

 known in Ireland. The great variet}^, however, of Fenestellid 

 species now established in the United States makes a more 

 thorough examination of our Carboniferous forms desirable. 

 Specimens showing outer coats, even if these resemble parasitic 

 crusts, are of especial value, and may possibly furnish new 

 examples of the beautiful He^nitrypa series. Even in museums, 

 a large number of Fenestellid specimens are merely casts of 

 various parts of the zoarium ; and at any time some choice 

 example may be discovered, which may largely improve our 

 knowledge of a genus. The observation of the "eight radial 

 denticles," pointing inwards from the mouth of the zooecia, in 

 Actinostoma,- was a striking step forward in this direction, and 

 similar structures may have existed in many Fcnestellce or 

 Polyporce. The controversy, again, as to the nature of 

 Patceocoryfie^ shows how even important appendages of these 

 complex polyzoa may be lost from all . but the most 

 exceptional specimens. Too often, moreover, workers have 

 been glad to set aside such discoveries as "abnormalities" 

 and "parasitic growths," without going to the length of sup- 

 porting their assertions by a section. A great deal can be 

 learned of the structure of a Fenestellid zoarium by merely 

 grinding down two surfaces perpendicular to one another and 

 to the face of the zoarium (vertical and horizontal sections), 

 and examining these, when moistened, with a dissecting 

 microscope or even with a hand-lens. 



The Fenestellidae have hardly yet revealed all their secrets 

 to us. Their zooecia, as is now known, depart widely from the 

 simple cyclostomatous type, and Ulrich,^ with great reason, 



1 "The Localities of the Irish Carboniferous Fossils," /^w^«- Geol. Soc. 

 Dublin^ vol. ix. (1S60-62), p. 53. 



- Prof. J. Young and J. Young, " New Carboniferous Polyzoa," QuarL 

 Jotirn. Geol. Soc. London, vol. xxx (1874), p. 681. 



^ Ibidf p. 684. Nicholson and Lydekker, op. cit., p. 624. 



* Oj>. cit.y p. 344. 



