the Palaeozoic Bivalved Entomostraca. 417 



ton Limestone ; but in 1852 (Brit. Pal. Foss. Camb. Mus. Ap- 

 pendix A, p. ii.) he decided to call it B. strangulata. 



Schrenk recognizes this species in the brown bituminous marl 

 (Brandschiefer) of the Lower Silurian of the Baltic Provinces 

 (Untersuch. p. 195). 



1*. Primitia strangulata, Salter, sp., var. a. 

 Beyrichia strangulata, var. a, ibid. p. 172, pi. 6. fig. 19. 



Differing from the foregoing chiefly by the furrow being faint 

 and extending far across the valve. In fossiliferous schist (Lower 

 Silurian) at Robeston Wathen, Pembrokeshire. 



2. Primitia Salteriana, no v. 

 Beyrichia strangulata, var. /3, ibid. fig. 20. 



This differs from P. strangulata in the absence of the raised 

 rim, in the more acute anterior extremity, and in the punctation 

 of the surface. In fossiliferous schist (Lower Silurian), Sholes 

 Hook, Haverfordwest. 



Schrenk speaks of this variety (but with papilla? instead of 

 pits) as occurring in the Lower Silurian Brandschiefer and 

 Borkholm beds of the Baltic Provinces (Untersuch. p. 196). 

 He also refers to another form ("var. crenulata"), with a broad 

 and notched border, from the Lower Silurian beds at Paggar 

 and Borkholm (Untersuch. p. 196). 



3. Primitia semicordata, nov. 

 Beyrichia strangulata, var. /3, young, ibid. fig. 21. 

 Besides being smaller than any of the above, this is relatively 

 short and broad, nearly semicircular, and smooth. Accompany- 

 ing the last mentioned. 



4. Primitia simplex, Jones. 

 Beyrichia simplex, ibid. figs. 25, 26, 27. 

 This small, smooth, subovate species was first observed in the 

 Lower Silurian schist of Busaco, near Coimbra, Portugal ; and 

 the very slightly different forms from a Lower Silurian schist 

 at Harnage, near Shrewsbury, do not appear to be separable 

 from it. 



5. Primitia Logani, Jones ; et varr. 



Beyrichia Logani et varr. reniformis et leperditioides, Ann. Nat. Hist. 

 ser. 3. vol. i. p. 244, pi. 9. figs. 6-10. 



A large number of this gregarious species comprise so many 

 variations of form, from oblong to reniform, on one hand, and 

 from oblong to subovate, on the other, with or without puncta- 

 tion of surface, but always sulcated, that it seems impossible to 

 draw any lines of distinction, excepting such as may limit the 



Ann. $ Mag. N. Hist. Ser. 3. Vol. xvi. 28 



