Corals and Bryozoans of the Lower Helderberg. 147 



which are perforated at regular distances by large pores, distant from each other 

 less than the diameter of the tube, generally a single series on each face of the 

 wall ; transverse plates rather closely arranged. 



From the globular form of this small species, and where the external charac- 

 ters are obscured by shale, it may be mistaken for the species of Astylospon- 

 gia, found in the same rocks. The largest specimens observed are about four 

 centimetres in diameter. 



Formation and localities. In the shaly limestone of the Lower Helderberg 

 group, near Clarksville, and Catskill creek, N. Y. 



Favosites minimus. 



(PLA.TE VII, FIGS. 1-12.) 



Favosites? minima, Hall. Twenty-sixth Rep. State Mus. Nat. Hist., p. 113. 1874. 



Corallum massive, variable in form. Cell-tubes small, polygonal, generally 

 hexagonal, from two to thirteen mm. or more in length ; diameter .25-. 35 mm. ; 

 there are numerous maculae where the cells are larger than the others, being 

 about .50 mm. in diameter. Cell-walls thin, more or less corrugated and stri- 

 ated transversely ; septa strong, distant from each other a space equal to two or 

 three times the diameter of the tube ; mural pores minute, comparatively dis- 

 tant, a single series on each face of the tube. 



This species is very variable in its mode of growth, sometimes occurring in 

 branching forms, with the cell-tubes commencing at the centre, and gradually 

 curving upward and outward to the surface ; others are in hemispherical 

 masses, with a flat base, the tubes radiating from the centre of the base to the 

 surface ; increasing by interstitial or lateral additions ; sometimes in masses 

 formed of successive layers as if by interruptions in growth ; it is also found 

 incrusting crinoid stems and other objects, especially the basal portion of 

 Lepadocrinus, occurring in layers of sometimes not more than two mm. in 

 thickness. 



It differs from F. proximus in its smaller cell-tubes, the thinner walls, and 

 the frequent maculae of larger cells. 



Formation and localities. Lower Helderberg group, Schoharie, and near 

 Clarksville, N. Y. 



Favosites proximus, n. sp. 



(PLATE VII, FIGS. 13-15.) 



Corallum forming irregular masses ; cell-tubes polygonal, of nearly uniform 

 size ; diameter slightly more than .50 mm. ; transverse partitions strong, gen- 

 erally distant from each other a space equal to twice the diameter of the cell- 

 tubes, though frequently occurring much closer; mural-pores minute, occurring 

 in one or two series on each face of the tube. 



This species in general appearance is very similar to F. minimus, but may 

 be distinguished from that species by its larger cells, thicker and smoother cell- 

 walls and the absence of maculae of larger cells. 



Formation and locality. Lower Helderberg group, Schoharie, N. Y. 



