138 PALEONTOLOGY 



one pair of arms (genus Gomphoceras) or for three or four 

 pairs. 



6. Meloceras [Cyrtoceras] elongatum (Fig. 41, a) 

 is found in the Upper Silurian limestone of Bohemia. It 

 is compressed-elliptical in section and curved in form, the 

 curvature decreasing from youth to age (i.e., from apex 

 to body-chamber), and the plane of curvature being, that 

 of the major-axis of the ellipse. It attains a length of 

 80 to 90 mm. of which nearly a third is body-chamber. 

 The septa have the simple form seen in Ortliocems, but 

 are more closely set than in that genus, their distance 

 apart being only about one-sixth the major axis of the 

 cross-section. The siphuncle is close to the convex 

 margin, and forms a continuous calcareous tube, con- 

 stricted as it passes through the septa. The shell is only 

 ornamented by fine striae, the course of which shows 

 a very slight hyponomic sinus on the convex margin, 

 which is therefore ventral. Thus this species is exo- 

 gastric, and the siphuncle is ventral (its usual position 

 when not central). There are other species attributed to 

 the same genus which are endogastric. 



7. Cophinoceras [Gyroceras] ornatum is found in 

 the Middle Devonian limestone of the Eifel. Compared 

 with the last it has a stronger curvature, so that it forms 

 a complete spiral of at least a whorl and a half, but there 

 is no contact between the whorls. It is depressed- 

 elliptical in section (i.e., the long axis of the ellipse is at 

 right angles to the plane of coiling). The only ornament 

 seen on the cast is a paired series of rather coarse and 



