338 Proceedings of the Royal Society of Victorict. 



escaped compression. The upper half of the shell is marked by 

 a longitudinal median depression or fracture. 



The species itself was originally recorded from the Marcellus 

 shale, and the lower part of the Hamilton group, in the States of 

 New York and Indiana. 



Occurrence and Horizon. — This variety is found in great 

 abundance in the bluish-grey shales of McMahon's Creek (from the 

 Department of Mines, 3778). [1185 and 2357-60]. Also from 

 the hard blue shales at the mouth of Starvation Creek (Depart' 

 ment of Mines, 3368). [2361]. Both are from the Upper Yarra 

 district. Some of the rock specimens are largely composed of 

 these tiny shells. The latter are usually superficially stained by 

 limonite, which causes them to stand out in contrast to the matrix 

 of the rock. Siluro-devonian or Devonian. 



Genus Tentaculites, Schlotheim. 



Tentaculites matlockiensis, sp. nov. 



(PI. XXXI., Figs. 1, 2, 3, 5). 



Description. — Shell conical, tapering, but broader at the open 

 end than is usual in this genus. Shell substance thin, as in 

 Styliola, but having distinct annuli, as in the typical forms of 

 Tentaculites. Apical portion bulbous, sometimes apiculate, and 

 occasionally with an overhanging ilange. Margin of the orifice 

 undulate, and with a vertical slit or sinus in a line with the 

 median depression of the shell-surface. A transverse section of 

 the shell shows it to be thinner in the neighbourhood of this 

 depression, and the example figured (Fig. 5) has a tubular 

 enclosure which has the appearance of a small siphuncle or 

 ventral canal. The proximity of this tube to the wall of the 

 shell seems, however, to be unfavourable to the idea of its 

 relationship to the Cephalopoda, to which it might otherwise 

 point. On the other hand examples are not unknown where a 

 smaller shell is found enclosed in an adult specimen, and from the 

 relative diameter of our section, the slice was apparently 

 taken across the shell, not far from its apical end, where the 

 enclosed shell would have a much smaller diametei'. 



The first third of the shell is generally smooth, afterwards 

 becoming annulated with thin salient ridges, the intercostal 



