870 ON A NEW SPECIES OF RHIZOPHYLLUM. 



moderately thin, horizontal, with no signs of cardinal septum; 

 ventral margin thick at the centre, but tapering towards the 

 lateral angles, with a fossula on the inner side; a slight depression 

 externally showing the probable position of the counter septum; 

 the septa are present in the form of crenulations. A thick well- 

 marked laminar epitheca covers both dorsal and ventral surfaces. 

 The remains of a few exothecal processes or anchoring stolons are 

 visible on the ventral surface near the lateral angles. The inter- 

 nal structure is vesicular, the vesicles showing faintly at the 

 weathered fractured apex; these vesicles were rendered more dis- 

 tinct by grinding and polishing the apex. 



The measurements of the specimen are as follows : — Length of 

 the corallum | inch; greatest width across the calice ly^^-; greatest 

 thickness J inch. 



Locality and horizon. — Shales in DerrenguUen Creek at the 

 junction with Limestone Creek, near Yass; Upper Silurian, pro- 

 bably Wenlock; Coll. A. J. Shearsby. 



J propose to call this interesting coral Rhizofhyllwni yassense. 



EXPLANATION OF PLATE. 



RltizoplnjlluDi yassense, A. J. Shearsby. 



Fig. L — Dorsal view. 



Fig. 2. — Ventral view. 



Fig. 3. — Lateral view. 



Fig. 4. — View of calice, showing crescentic shape, the thick inturned ven- 

 tral margin with fossula, the subcentral depression, and the crenu- 

 lations. 



Fig. 5. — Dorsal view showing calice and fossula. 



Fig. 6. — View of apex. 



Fig. 7. — Weathered section of apex, showing vesicular tissue ( x 2). 



Note.— Figs. 1 to 6 are drawn natural size. Fig. 7 is twice natural size. 



