CEPHALOPODA. 157 



Subclass EUTHYNEURA 



Order Opisthobranchia 



Suborder Conulariida 



Family Tentaculitidae 



Genus Tentaculites Schlotheim 



Tentaculites sp. undet. 



Plate 39, figure 6. 



Fragments of Tentaculites are common in the St. Laurent limestone and are present 

 in the Beauvais sandstone. The fragments are too imperfect for specific reference. 

 The specimen which shows best is an impression .9 of a millimeter in diameter with 

 3 annulations per millimeter. The annulations are closer together than in any described 

 species and take up more of the space. This specimen is from the Beauvais sandstone. 

 The same species is found in the St. Laurent but another species in that formation has 

 much less prominent annulations. 



Class CEPHALOPODA 

 Subclass Tetrabranchiata 



Order Nautiloidea 



Suborder Orthochoanites 



Family Orthoceratidae 



Genus Orthoceras Breynius 



Orthoceras cf. subulatum Hall 



Plate 37, figure 10. 



1843. Orthoceras subulatum Hall, Geol. New York, Rept. Fourth Dist., p. 180, fig. 1. 



1861. Orthoceras subulatum Hall, Descriptions of New Species of Fossils, etc., p. 49. 



1862. Orthoceras subulatum Hall, 15th Rep. N. Y. State Cab. Nat. Hist., p. 77. 

 1879. Orthoceras subulatum Hall, Pal. New York, vol V, pt. 2, pp. 283-284, pi. 38, 



fig. 3; pi. 84, figs. 1, 2, 4, 6-10; pi. 86, figs. 1, 2. 

 1910. Orthoceras (Geisonoceras) subulatum Grabau and Shimer, North American Index 

 Fossils, II, pp. 52-53, fig. 1252, b. 



1912. Orthoceras cf. subulatum Kindle, Bull. U. S Geol. Surv., 508, p. 106. 



1913. Orthoceras subulatum Prosser and Kindle, Maryland Geol. Surv., Middle and 

 Upper Devonian, pp. 308-309. pi. 39, figs. 1, 2. 



Hall's description — "Shell straight, regularly enlarging from the apex to near the 

 aperture. Transverse section circular. Apical angle varying, in normal and com- 

 pressed specimens, from six to nearly eight degrees. Initial extremity observed, but 

 the characters are obscure. 



Chamber of habitation well developed, having a length equal to about three times 

 its diameter at the last septum, regularly expanding to a point near the aperture where 

 it is slightly contracted. Air chambers numerous, increasing in depth from the apex 

 to the outer chamber, where the depth is about three mm. 



Septa smooth, thin, having a concavity equal to an arc of about 125 degrees. 

 Sutures straight and horizontal, but little impressed on the internal mould. 



