BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 44I 



phuncle and then again outward thus producing contractions of the 

 siphuncular space between the septa. The siphuncular segments or 

 an endosiphohning however covers these funnels in such a way as 

 to leave a perfectly cylindric lumen of the siphuncle [see text fig. 



15]- 



Hyatt has placed his genus Protocycloceras under the suborder 

 Orthochoanites (with the Cycloceratidae). If the above stated ob- 

 servation of the structure of the ectosiphuncle of P . 1 a m a r c k i 

 is correct, that form is to be referred to the Holochoanites and to 

 be considered as an annulated endoceratid. Since we have found 

 exactly the- same condition of the siphuncle in other annulated forms 

 from the Beekmantown described below as P . w h i t f i e 1 d i we 

 Tiave no doubt that the endoceratid condition of the ectosiphuncle 

 still prevailed among these early annulated forms ; but that the 

 formation of endosiphosheaths had already ceased among them. 



We have then before us the alternative of either referring these 

 forms to Endoceras which according to Hyatt's definition embraces 

 '" smooth and annulated orthoceracones " and to let the genus Pro- 

 tocycloceras stand for orthochoanitic forms still to be discovered or 

 since P . 1 a m a r c k i has expressly been pointed out as the type 

 of that genus to alter the definition of the latter to suit the type speci- 

 men and other obviously closely related species and thus transfer the 

 term Protocycloceras to the annulated Endoceratidae. We \vould 

 propose the latter procedure as the one least liable to create con- 

 fusion. 



Protocycloceras lamarcki Billings (sp.) 



Plate 15, figure 1-6; plate 16, figure i, 2 

 O r t h o c e r a s lamarcki Billings. Can. Nat. & Geol. 1859. 4 1362, 



%• l g- 

 Orthoceras lamarcki Billings. Geol. of Can. Pal. Foss. 1865. 



1:25s, 347, fig. 336. 

 Protocj'cloceras lamarcki Hyatt. In Zittel-Eastman. Text-book 

 of Palaeontology, igco. i :5i8. 



Annulated orthoceratites appear already in rocks of the Spelman 

 ledge at Beekmantown which belongs to Seely's D of the Beek- 

 mantown formation. Unfortunately only sculpture casts are re- 

 tained in the crusts of friable sand which are left after weathering 

 of the dolomite, while the latter in its fresh state though extremely 

 hard and brittle shows but faint traces of these cephalopod remains. 

 The specimens found belong all to middle sized individuals. 



In the subcircular section, rate of expansion (about i mm in 20 

 mm) and slight curvature of the conch, the character of the annu- 



