the Pataozoic Bivalved Entomostraca, 419 



subcircular umbilical pit. The surface of the valves is dotted 

 with coarse shallow pits, and sometimes slopes gradually to the 

 margins, but is generally deflected abruptly. There is a slight 

 rim at the border. P. variolata is not far removed from P. sigil- 

 lata and P, Seminulum ; indeed, it may be said to be the British 

 representative of the former. From the Woolhope Limestone, 

 west of the Wych, Malvern. 



9*. Primitia variolata, var. paucipunctata, figs. 6c,6d. 



Length — H^, height -r%i^ inch. 



This bears fewer pock-marks, has a less well defined border- 

 rim, and a rather smaller sulcus. From the Woolhope Lime- 

 stone, west of the Wych, 



10. Primitia rugulifera, Jones. 



Beyrichia rugulifera, Ann. Nat. Hist. ser. 3. vol. i. p. 242, pi. 9. fig. 4. 



Oblong, ornamented with minute transverse wrinkles, and 



impressed with a broad and deep sulcus on the anterior half. 



From the Upper Silurian Limestone of Beechey Island, together 



with other small Bivalved Entomostraca. 



11. Primitia renulina, nov. PI. XIII. figs. 5 a, 5 b. 



Length -t^, height -jV (^^ 3 to 2), thickness Vt inch. 



Carapace convex, ovate-oblong, straight on the back, boldly 

 curved on the other margins, especially backwards; dorsal 

 angles distinct; anterior region compressed. Valves smooth, 

 bilobed, impressed with a deep well-defined dorsal sulcus, and 

 bordered all round with a narrow depressed rim, which runs 

 into the sulcus at the back or upper part of the valve. From 

 the Wenlock Limestone at the Crofts, Malvern. 



12. Primitia mundula, Jones. 



Beyrichia mundula, Ann. Nat. Hist. ser. 2. vol. xvi. pp. 90 & 174, pi. 5. 

 fig. 23, & pi. 6. figs. 28-31. 



In addition to the diagnosis of this neat little species given 

 at p. 174, op. cit., we have to allude to the swelling of the sides 

 of the sulcus in some well-grown individuals, which, however, 

 are not specifically distinct from others with less developed 

 sulcus, — also to the beautifully delicate reticulated sculpture of 

 the surface, which sometimes appears as excessively fine longi- 

 tudinal wrinklings, with inosculating meshes, and sometimes as 

 a minute pitting. 



Small individuals (long ^, high ^ inch) are more oblong 

 than others, having rounded ends, parallel upper and lower 

 borders, and a faint sulcus. The normal form approaches that 

 of Leperditia ; and, with a short hinge-line, angular ends, and 

 convex belly, the valves become almost oval. P. mundula has 



28* 



