﻿494 



There is obviously a great variation in the coiling of the shells of 

 this transitional species as is shown by Barrande's figures. One shell 

 has no contact furrow at a very late substage of development. It 

 is possible, however, that there are several species included under 

 this name. 



A slight impressed zone or flattened dorsum is retained in the 

 gerontic stage. Considering the slight coiling of the shells, this 

 fact is important. 



Anomaloceras. 



This genus was described in Genera of Fossil Cephalopods, p. 283, 

 and includes nautilian forms having close-coiled young with a small 

 umbilical perforation. The whorls are depressed oval, kidney- 

 shaped or digonal with a deep impressed zone. The sutures are 

 almost straight, or with slight ventral and lateral lobes. 



The siphuncle is subventran, and in the type is always laterad of 

 the mesal plane. 



Anomaloceras anomalum. 



Nautilus anomalus, Barr. (PL xxxiv). PI. vii, Figs. 16-20. 

 Loc, Bohemia. 



This species possesses very closely coiled whorls, and is of great 

 interest in connection with the history of the impressed zone, as is 

 demonstrated by the sections given on PL vii. These sec- 

 tions began with Fig. 16, which passed through the larger end of 

 the comma-shaped umbilical perforation. The paranepionic sec- 

 tion just below the centre is distorted slightly by the obliquity of 

 the direction of the cut, and has a septum crossing it just below the 

 siphuncle, and this organ is excentric and not so near the venter as 

 in the later stages. The section of a volution above the perforation 

 is also paranepionic, but older, and shows rapid expansion in lateral 

 diameters and a tendency to assume the nephritic outline, and has 

 in correlation with this a very slight dorsal furrow. The lateral 

 asymmetry of this whorl is probably in part due to a slight obliquity 

 of the section. The siphuncle is subventran as in all later stages. 

 The metaneanic substage appears in the second outline of a volu- 

 tion below the perforation, and this has a digonal nephritic form. 



This becomes trapezoidal and more rounded in the sections of 

 the outer ephebic volutions above and below those described above, 

 and in the full-grown specimens of some shells may become a much 



