REPORT OF THE STATE PALEONTOLOGIST I9O3 3I3 



into the angles [pl.8, fig.7] and the continuation of the angles into 

 the supporting membranes indicate that the latter already supported 

 the visceral cone before the formation of the last endosipho- 

 sheath, determined the form of the latter and at the time of its forma- 

 tion probably became the situs of organic deposits of lime carbonate. 

 This latter view is at least suggested by the presence of cavities 

 between the well defined bands of lime in the section. 



If these membranes served as suspensory organs of the visceral 

 cone and its posterior extension, their arrangement will give us a 

 hint as to which side of this Cameroceras conch was the ventral side 

 or turned habitually downward in the moving animal, the position 

 of the siphuncle on one side of the conch not being a reliable criterion 

 on account of its shifting sometimes in the same individual. It 

 will now be noticed that in the sections reproduced in plate 8, 

 figures 5, 6, the tube is suspended by three membranes, two of which 

 form a diameter of the siphuncle, parallel to its flat side, while 

 the third holds a perpendicular position to this diameter and 

 connects the tube with the side of the siphuncle diametrically 

 opposite to its flat side. If now a tube is suspended by means 

 of three membranes, forming an inverted T, it is evident that 

 the middle was the upper one. The alternative possibility that 

 the tube was held by props or propping blades instead of by 

 membranes, in which case the relation of the three blades would 

 be inverted, may be neglected on account of the evident thinness 

 and frailty of the supporting organs. It then follows that the 

 flat side of the siphuncle which is in contact with the conch was 

 the lower or ventral side. 



4 Comparison of endosiphuncular structures in Vaginoceras belcm- 

 nitiforme and Cameroceras brainerdi 



Holm's elaborate description of the endosiphocoleon of 

 Vaginoceras (gladius) belemnitiforme permits 

 a close comparison of the development of this organ in the 

 Swedish type and in this American form. 



In the description of the endosiphocoleon of V. b e 1 e m n i t i - 

 forme a distinction [/. c, p. 14] is made between the lateral and 



