ACTIXOCEKATID^. 
165 
usually more arcuate than in Ortlioceras ; the necks very short and 
recurved, and often with crystahine deposits (“ the auneaux ob- 
structeurs ” or “ depot organique,” of Earrande), which sometimes 
fill the spaces in the siphuncular cavity not occupied by the endo- 
siphon and its canals. SijDhuncle very large, the diameter sometimes 
equalling half that of the shell : much inflated between the septa, 
so as to present a series of segments of a compressed-globular form 
rig. 22. 
Pig. 23. 
Fig. 22, 1. Front view of a weathered fragment of the apical extremity of Actino- 
ccras Bigshyi ?, showing (/) the large foramen and the row of minute fora- 
mina situated atF, the most elevated part of the siphuncular segments. 
Fatural size. From the Black Eiver Formation (?), Igloolik Island, Arctic 
America. 
Fig. 23. View of part of a much eroded fragment of an Actinocems, consisting 
of the internal cast of some of the septal chambers, and the siphuncular 
segment with its foramen (/). f nat. size. Fig. 22, 2. Side view of part 
of the same specimen, showing the lateral position of the large foramen (/) 
in relation to the apex. Natural size. From the Great Slave Lake, British 
Is orth America. 
1 These are called “rosettes” by Hyatt, who regards them as “ internal or 
extra-endosiphonal deposits, and the successive sections of the outer wall of the 
siphon as strictly homologous with the successive sheaths of the endosiphon of 
Biloceras and Endoceras” (Proc. Boston Soc. Hat. Hist. 1883, vol. xxii. p. 271). 
