BEEJCMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 487 



Loxoceras moniliforme Hall (sp.) 



Plate 34, fig. 6-9 



Orthoceras moniliforme Hall. Pal. N. Y. 1847. ^'-35, pl- 7. 



fig- 5 

 Orthoceras su bare u at urn Hall. Pal. N. Y. 1847. v. t, pi. 7, tig. 



3 (apical part of type specimen) 



Description. Slender orthoceracone of circular section and mod- 

 erate size, attaining- a length of loo mm or more and a width of 

 17 mm; the rate of growth being 3 mm in the space of 20 mm. 

 The cameras are relatively deep, the septa being 4 mm apart where 

 the conch has a width of 12 mm; 2.5 mm apart where it is 

 8 mm wide. A slight organic deposit is found in the apical 

 cameras [see fig. 9]. The living chamber was large and may 

 have occupied fully one half or more of the conch. The aperture 

 is not known. The septa are shallow, their concavity not amount- 

 ing to one half the depth of the cameras and decreasing in 

 depth in apertural direction. The sutures appear to be straight 

 transverse. The siphuncle is large, its greatest width being nearly 

 one fourth that of the conch, propiocentren, nummuloidal, the inter- 

 septal segments spherical and empty as far as observed. The surface 

 was smooth or marked with growth lines only. 



Position and localities. Hall records his specimen to have 

 been obtained from the limestones at Chazy with M a c 1 u r e a 

 m a g n a ; our specimens were collected at Chazy in B^ (the upper 

 part of the middle Chazy or Maclurea beds) ; one was also found 

 by Prof, van Ingen at Plattsburg in the Saranac river and one has 

 been obtained in the upper Chazy (Cq) at Chazy village. 



Observations. The original drawing of this species is very 

 poor, for the siphuncle is drawn incorrectly and the septa, which in 

 the type are well shown, have been left otit altogether. We have for 

 this reason, with the kind permission of Prof. Whitfield, refigured 

 the type which is in the American Museum of Natural History. 

 It represents a natural section which in the apical region passes 

 near the ventral margin and therefore intersects the siphuncle, and 

 in the middle part of the fragment crosses obliquely to the dorsal 

 margin. To this oblique fracture the subparallel margins of the 

 upper portion of the type are due. The siphuncular segments are, 

 as our drawing shows, considerably more inflated than in the original 

 figure and agree well with those of the fossils referred to this 

 species on plate 34. Since also the rate of growth and the depth 

 of the chambers are identical, there can be no doubt of the correct- 



