PAL^ONTOLOG V. 3 1 



opment of lateral pores are sufficient to prove the Favosites type 

 of the species. The larger tubes are always lined with a cycle of 

 twelve rows of horizontal squamae ; the smaller tubes are usually 

 smooth, or exhibit only rudimentary squamae. The diaphragms 

 of the larger tubes are compound, by complication with the 

 squamae ; in the smaller tubes the diaphragms are simple ; all the 

 tubes are connected by abundant lateral pores disposed in longi- 

 tudinal rows. The orifices in certain spots of the surface are often 

 found closed by opercula. 



Found in the upper Helderberg strata of Mackinac and in the 

 drift deposits of the Lower Peninsula ; also abundantly occurring in 

 the corniferous limestone of Canada, New York, Indiana, and 

 Kentucky. 



Plate VIII. — Fig. 4 is a silicified specimen from the drift of 

 Ann Arbor. 



Plate XV. — Fig. 3 is a reticulated branching variety found at 

 the Falls of the Ohio, kindly lent to me by Dr. James Knapp, of 

 Louisville. 



I have from the same locality some subramose specimens of simi- 

 lar structure, but with larger tubes in contiguity and fewer in- 

 terstitial smaller ones. These form a transition link to another 

 species to be described hereafter (Favosites radiciformis). 



• FAVOSITES TUBEROSUS, N. Sp. 



Compare Favosites Troostii, Milne-Edwards, and FAVOSITES 

 BASALTIFORMIS PARS, Goldfuss. 



Tubes rounded-polygonal, unequal in size, variable, between two 

 and three millimeters in diameter, with larger tubes up to five 

 millimeters occasionally intermingled. A cycle of twelve longitu- 

 dinal rows of stout, horizontal squamae lines the inner circumfer- 

 ence of the tubes. The squamae of the joining rows alternate in 

 position, are not separated by intermediate furrows, but often 

 slightly interlock with each other. Pores large and very numerous, 

 two or three rows on each side, surrounded by a small pit instead 

 of a projecting rim, and one of them is generally situated directly 

 beneath each of the squamae. 

 17 



