CORALS AND BRYOZOA. 11 



ALVEOLITES, Lamarck. 1801. 

 Alveolites explanatus. 



PLATE XIII, FIGS. 15, 16. 

 Alveolites explanatus. Hall. Report of State Geologist for 1883. Expl. pi. 13, figs. 15, 16. 



Corallum growing a>s irregular incrusting expansions upon other organisms. 

 Cell tubes small, less than 1 mm. in longest diameter, compressed and rising 

 very obliquely to the surface; marked by obscure longitudinal striae. 



The specimens of this species which have been observed, occur in explanate 

 masses on Favosites and Stromatopora, and seldom weathered so as to exhibit 

 their exterior structure, but are usually shown in sections and polished cuttings. 

 It presents very little detail of form or structure, and is of little interest except 

 as being the only species of the genus noticed from the rocks of this age. 



Formation and localities. In the lower Pentamerus limestone of the Lower 

 Helderberg group, near Cedarville, Herkimer county ; near Clarksville, Albany 

 county, and at Schoharie, N. Y. 



CHiETETES, Fischer. 1837. 

 Ch.«tetes colliculatus. 



PLATE Vni, FIGS. 1-t. 



Chatetes collictdatwt. Hall. Thirty-second Rept. N. Y. State Mua. Nat. Hist., p. 148. 1879. 

 " " " Report of SUte Geologist for 1882. Expl. pi. 8, figs. 1-4. 1883. 



Corallum hemispheric. Base generally flat ; sometimes very concave, in 

 which case the corallum consists of a depressed conical mass. Base covered 

 by a strongly wrinkled epitheca. Cells polygonal, from quadrangular to 

 hexagonal, nearly equal in size; diameter at the aperture about .50 mm.; 

 walls thin and slightly undulating. Septa very thin, distant, five in the 

 space of 5 mm. Surface marked by inonticulae about 2 mm. in height, the 

 centers of which are distant from each other 5 mm., with cells the same 

 size as the others. 



The largest specimen observed has a diameter at the base of 35 mm., and 

 a height of 25 mm. 



