1865.] BILLINGS — PALAEOZOIC FOSSILS. 429 



perhaps, belong to the genus Protarcea. Gamache Bay, Anticosti ; 

 Division 3 ; Anticosti group; Middle Silurian. T. C. Weston. 



Genus Favosites, Lamarck. 

 F. prolificus. — Corallum forming large hemispheric or irregu- 

 larly convex masses. Tubes about one line in diameter. Tabulae 

 thin and either complete or imperfect, sometimes filling the tube 

 with vesicular tissue. They are often very numerous, there being 

 sometimes six or seven in one line. No septa or mural pores have 

 yet been detected, and it may be that this species should be placed 

 in another genus. Hudson River group and throughout the 

 Middle Silurian; Anticosti. J. Richardson and T. G. Weston. 



Genus Stenopora, Lonsdale. 

 S. bulbosa. — This species is found in small globular or sub- 

 pyriform masses from six to thirty lines in diameter. There is 

 often a small shell buried in the base. The tubes are about the 

 size of those of S. petrojjolitana. Gamache Bay, Anticosti ; 

 Division 1; Anticosti group; Middle Silurian. 



Genus Petraia, Munster. 



P. Ottawaensis. — Turbinate and either straight or more 

 or less curved, enlarging to a diameter of about an inch 

 in a length of two and a-half inches, irregularly constricted at vari- 

 ous intervals and usually engirdled with fine wrinkles. There are, 

 apparently, about fifty principal septa with smaller ones between, 

 where the diameter is about one inch. Cup, nine lines in depth. 

 Differs from P. corniculum in the irregularity of its surface. 

 Ottawa, Trenton formation. E. Billings. 



P. selecta. — Base acutely pointed ; above, rather slender for 

 the first few lines, then more rapidly enlarging. Depth of the 

 cup about two- thirds of its width at the margin, septal striae four 

 or five in two lines. The plane of the margin of the cup is, in all 

 the specimens I have seen very oblique, always inclining towards 

 the curved side. Length of largest specimen seen fifteen lines ; 

 width of cup twelve lines. In general, the individuals are more 

 slender. West end Lighthouse, in the Hudson River formation ;. 

 also at Gamache Bay, Anticosti ; Division 1 ; Anticosti group; 

 Middle Silurian. 



P. pulchella. — The two specimens on which this species is 

 founded are acutely pointed and moderately curved. The following 

 are their dimensions. One of them is nine lines in length and six 



