Palceozoic Bivalved Entomostraca. 405 



1**. Var. simplex, nov. (PI, XII. figs. 4 a, 4 h.) 

 Proportions :— L. 21. H. U\. Th. 9. 



The ridge of the plateau in this neat and rather small cara- 

 pace is perfect all round the oval bounding the median hollow, 

 but ventrallj it has a triangular promontory pointing inwards, 

 and analogous to the ventral modifications of figs. 2 and 3. • 



Two specimens : — Vine Coll. no. LXVig, 13. Tickwood Beds. 



1***. Var. informis, nov. (PI. XII. figs. 5 a, 5 l.) 

 Proportions:— L.. 20. H. 11^. Th. 11^. 



Oval in outline and subquadrate in edge view. The oval 

 ridge ventrally is continued inwards bj a thickening, which is 

 at first curved and then stretched across to the dorsal part of 

 the ridge, thus dividing the valve-surface into two irregular 

 hollows, of which one is simply a curved sulcus, and the 

 other is like a long and thick inverted comma. 



One specimen : — Vine Coll. no. LXVI5. Tickwood Beds. 



1****. Var. hipartita, nov. (PI. XII. figs. 6 a, 6 h.) 



Proportions :— L. 29. H. 17. Th. 13^. 



Here within the ridge is a short cross ridge nearly in the 

 middle, connecting the two sides and making a pattern like 

 that of a strong chain-cable. In some individuals (liii.) the 

 valves are shorter and the two hollows rounder and nearer 

 together, thus becoming more truly like a figure-of-eight. 



fVine Coll. no. Lll. "i ^ -, ,^ cii i 



,,,, f Bed no. 46. Shale over 



). LII. ^ 

 LIII. y 

 LVII. j 



Nine J "^' C Wenlock Limestone, 



specimens : j ^^^^ gj^^j^ .^^^^ Wenlock 



l^ Limestone. 



1*****. Yax. persona, nov. (PI. XIL figs. 7 a, 7 h.) 

 Proportions :— L. 22|. H. 16. Th. 12. 



Carapace relatively short and high, the dorsal edge being 

 nearly semicircular, and the ventral almost straight. The 

 plateau is divided by a cross ridge, and a semicircuhir hollow 

 remains on one side (posterior) ; while on the other there are 

 three smaller hollows due to subdivisions by a small furcate 

 ridge. Looked at in one direction (front end upwards) it 

 shows a mask (persona), two round hollows representing the 

 eyes, beneath which are the signs of nose and mouth. 



One specimen : — Vine Coll. no. Llii. Bed no. 46, 



