362 MESSES. H. A. NICHOLSON AND R. ETHEEIDGE 



lamelUco7'ms from the Upper Silurian of "Wisby ; and after a careful 

 microscopic examination of its characters, we are enabled to en- 

 tirely confirm his description. "We have also fully examined two 

 ~ corals from the Devonian of North America, which were originally 

 referred to Alveolites, but which we find to be essentially identical 

 with Pacliifpora, and therefore to be properly referable to this 

 genus. The corals in question are Alveolites Fisclieri, Billings, 

 and A. frondosa, Nich. 



A. Msciieri, Bill., agrees in all important points with Pachypora 

 lamellicornis, Lindstrom, though specifically distinct. It forms 

 flattened expansions or fronds, rarely incrusting foreign bodies, 

 from one to four lines in thickness, and often of considerable size. 

 The corallites are disposed obliquely to the surfaces, diverging in 

 opposite directions from a central plane, and opening by distinct 

 calices on both aspects of the frond. The walls of the corallites 

 are thickened as they approach the surface, and are formed of 

 numerous delicate concentric laminae where they surround the 

 calices. The calices are oval or rounded, often semilunar, remote, 

 and neither exhibiting a single septal tooth nor rudimentary spi- 

 niform septa. The walls of the corallites are perforated with a 

 few remote mural pores of large size ; and the tabulae are either 

 absent or are few and remote. 



In all the above characters A. Fischeri agrees with Pae7ii/pora 

 lamellicornis, save in wanting the comparatively numerous rudi- 

 mentary septa which can be observed in well-preserved examples 

 of the latter. We have no hesitation, therefore in referring the 

 two to the same generic group ; and A. Fischeri must in future 

 stand as PacJiypora Fischeri. 



Alveolites frondosa, JSTich., also from the Devonian of ISTorth 

 America, agrees in all the essential features of its organization with 

 the preceding, and must therefore be removed to the genus Pa- 

 chypora. It differs from P. Fischeri, however, in the compara- 

 tively small size of the corallites, and the fact that the calices are 

 distinctly semilunar or sub triangular, often curved and fissure-like. 

 In well-preserved examples also there are indications of the 

 existence of two small tooth-like inward projections of the lower 

 lip of the calice, thus establishing a passage between Pachypora 

 and the forms generally referred to Goenites, Eichw. The mural 

 pores appear to be few and remote ; and we have been unable to 

 detect tabulse in longitudinal sections of this species. 



Group D. Alyeolites septosa, Fleming. 

 Our specimens of this species form hemispherical or pyriform 



