REPORT OF THE STATE PALEONTOLOGIST I903 333 



clusively ainswer. But the fact that the endosiphocoleon is also here 

 in the earHest successive sections of the siphuncle [see pl.ii, fig. 5, 6] 

 supported either by continuous membranes proceeding from its 

 corners or by longitudinal series of closely arranged endosipho- 

 funicles would argue for a derivation of the endosiphofunicles from 

 the endosiphoblades. That indeed in the apical portion of the 

 siphuncle one of the two mentioned modes of suspension prevailed 

 is to be inferred from the fact that in the above cited succeeding 

 sections^ — and as well in the sections found on the other side of the 

 cutting planes and separated from them by about imm^ — the dark 

 lines which are the sections of the suspensories, retain the same 

 position throughout. 



The arrangement of the endosiphofunicles and endosipho- 

 blades in the sections [pl.ii] shows quite conclusively that the 

 side of the siphuncle which is the upper in the drawings was 

 also the upper side during the life of the animal. In the longi- 

 tudinal section [pi. 13, fig-3], which exhibits a series of endo- 

 siphofunicles the direction of the latter is of still further interest 

 as giving a hint as to the direction in which the animal carried 

 its conch. We notice that if we give the endosiphofunicles a 

 perpendicular position, such as they should have according to 

 their function as suspensories the conch assumes a direction 

 which is obliquely ascending under a small angle. This stands in 

 full accord with what we know thus far as to the dorsal and ventral 

 sides of the animal ; the siphuncle being in contact with the ventral 

 wall of the conch, while the chambers form on the upper (dorsal) 

 and lateral sides.^ The fact brought out by the outline of a large 

 specimen given by Whitfield that the ventral side is nearly straight^ 



membrane of the septal chambers; while Hyatt [1883, p. 272] believes 

 with Barrande that they did not penetrate the true external wall of the 

 siphuncle. If Barrande and Hyatt are right in this contention and 

 Hyatt also in his view that the " rosettes " or endosiphuncular deposits 

 of Actinoceras are strictly homologous to the endosiphosheaths of Endo- 

 ceras and Piloceras [1883, p. 27] the endosiphofunicles of Piloceras 

 explanator may indeed be homologous to the " tubuli," and their 

 function identical, viz, that of suspensories for the siphon, whose outer 

 membranes have become calcified. 



^In the section the chambers of course appear only on the upper 

 (dorsal) side. 



