BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 43 1 



On account of the dorsal position of the siphuncle, its large size, 

 apparent tubular segments and its supposed filling with organic 

 carbonate of lime, we have brought this species under Cyrtendoceras 

 which according to Hyatt is the only genus containing holochoanitic 

 cephalopods with coiled conchs. The characters of the early 

 volutions of this primitive and interesting species are unfortunately 

 not sufficiently well preserved to allow satisfactory investigation. 



This cephalopod bears in its general appearance considerable 

 similarity to a gastropod that is very common in the same beds 

 and has been identified by Whitfield with Ma clurea sordida 

 Hall. It can, however, always be distinguished from the latter by 

 its evenly rounded volutions. 



Suborder D. ORTHOCHOANITES Hyatt 

 Division I. ORTHOCERATIDA 

 Family orthoceratidae 

 Genus baltoceras Holm 

 Baltoceras (?) pusillum, sp. nov. 



Plate 9, figure 4, 5 



A single specimen of this form was obtained which has furnished 

 us the data for the following description. 



Description. Small orthoceracone (length of imperfect speci- 

 men 32 mm), which expands very gradually (rate I mm in n mm), 

 section subcircular or slightly elliptic (?). Septa straight, trans- 

 verse, relatively distant (6-7 in the space of 10 mm), little convex, 

 (curvature of septa not more than one fourth the depth of the cham- 

 bers). Siphuncle very wide, one half the width of the conch, begin- 

 ning with a slightly curved apical portion, which is completely in- 

 closed within the phragmocone, situated excentric (subventran ?) , 

 its walls composed of very short funnels and long tubular siphuncu- 

 lar segments. Living chamber not known ; the surface appears to 

 have been smooth. 



Position and locality. In bed A 3 (Fort Cassin beds) of Yalcour 

 section. 



Observations. This little form of which we unfortunately have 

 not been able to secure sufficient material for more complete in- 

 vestigation, is remarkable for two features. These are the great 

 width of the siphuncle and its excentric position. In both of these 

 characters the species differs from a typical Orthoceras and 

 shows its more primitive state of development. It would by its 

 wide siphuncle suggest its relationship to the Endoceratidae, but the 



