41» Prof. T. R. Jones and Dr. H. B. Holl on 



oblong forms to P. Logani proper (whether long-oblong or 

 ovate-oblong), — dividing off the kidney-shaped valves as var. 

 reniformis, and those that have the most sloping dorsal angles 

 as var. leper ditioides. They all come out of a Lower Silurian 

 limestone (upper portion of the Calciferous Sandrock) at Gren- 

 ville and Hawkesbury, Canada. 



6. Primitia matutina, nov. PI. XIII. figs. 7a, 7 b. 



Length two, height -j^^ inch. 



This small, smooth, convex, Leperditia-%]i?L^&di, non-sulcated 

 Primitia might be catalogued as a variety of B. Logani, had we 

 ever seen a specimen of the latter without a sulcus, or with an 

 inclination to lose its furrow. Under existing circumstances, 

 however, we give the benefit of the doubt, and the value of 

 geographical distance, such as it is, to the probability of this 

 little Lower Silurian form being distinct from its Canadian ally. 

 The Trinucleus-shale (belonging to the upper part of the Bala 

 or Caradoc formation) in the river Onny, near Cheney-Longville, 

 Shropshire*, abounds with such small Entomostraca as this 

 Primitia ; but we have been able only to pick out this form in 

 a well-preserved state. 



7. Primitia Seminulum, Jones. 

 Beyrichia Seminulum, Ann. Nat. Hist. ser. 2. vol. xvi. p. 173, pi. 6. fig. 24. 

 A neat little semicircular form, from the Upper Silurian 

 schists of Montgomery, where it occurs with Beyrichia Klcedeni. 



8. Primitia sigillata, Jones. 



Beyrichia sigillata, Ann. Nat. Hist. ser. 3. vol. i. p. 242, pi. 9. fig. 5. 



More oblong than P. Seminulum, less deeply furrowed, and 

 somewhat more coarsely punctate. From the Upper Silurian 

 Limestone of Beechey Island, with P. rugulifera, P. muta, and 

 Leperditia gihhera. P. variolata is the British representative of 

 P. sigillata. 



9. Primitia variolata, nov. PI. XIII. figs. 6 «, 6 6. 



Length -2^^, height t-^l£_ (as 3 to 2). 



Carapace moderately convex, varying between suboval and 

 subquadrate ; rather more obtuse behind than before. Hinge- 

 line straight, but somewhat overhung by the dorsal part of the 

 valves. Valves somewhat flattened, impressed with a distinct 

 dorsal sulcus, which ends, towards the middle of the valve, in a 



* An account of this Trinuclens-shale is given in a paper by Messrs. 

 Salter and Aveline, Quart. Journ. Geol. Soc. vol. x. p. 62, &c. See also 

 ' Siluria/ 2nd edit. p. 72, &c. The Caradoc and Bala beds are regarded as 

 belonging to a higher horizon than the Calciferous Sandrock of Canada, 

 in which P. Logani abounds. 



