220 Prof. T. R. Jones and Dr. H. B. Holl on 



2. Primitia bipunctata, Salter, sp. Woodcut, fig. 5. 



Bcyrichia bipunctata [Salter, MS.], Catalogue Foss. Mus. Pract. Geol. 

 1865, p. 10. 



Mr. J. W. Salter, F.G.S., long ago supplied one of us with 

 specimens of black Llandeilo Flagstone (from Hellpool, Wye- 

 forth, near Builth, in South Wales), bearing numerous im- 

 pressions and casts of minute 



subquadrate Entomostracan , \ 



valves, each having two little i c; \ 



pits near the straight edge. \ / 



The features are obscure, and 



the specific characters necessa- ~^- ~" 



rily indefinite ; but we wish to Fi "- 6 ' Primitia hi P"™M«- 

 place this little Lower- Silurian 0lltlme of "^tvalve,from a sealing- 

 J, i •,! p wax cast ot an impression. 



form on record, with a figure, (Magnified about 20 diameters.) 

 among its allies. 



About a year since, George Reece, Esq., Secretary and 

 Curator of the Worcester Museum, submitted to us for exami- 

 nation a small piece of greenish micaceous shale, collected by 

 himself from the Ludlow beds of Abberley (probably from the 

 middle or Aymestry part of the series), containing Polyzoa, 

 small Brachiopods, one valve of Primitia ovata, J.&H., two or 

 three of P. renulina, J. &H., and several valves of a semi- 

 circular Primitia, small and white, of rather variable shape 

 (much crushed), marked with either a single pit, a slight lon- 

 gitudinal sulcus, or two distinct pits near the straight margin. 

 The bipunctate condition reminded us of Mr. Salter's Beyrichia 

 bipunctata from Builth ; but, on careful examination, we find 

 that the two pits are due to the wearing away of some of the 

 valve-substance where it is most convex on either side of the 

 single, longitudinal, furrow-like pit in Primitia umbilicata. 



Figs. 6 a and 6 b (PI. XV.) indicate two of the most distinct 

 of the little specimens, whereby the varying curve of the extre- 

 mities and ventral border, and the unequal sinuosity of the 

 nearly straight dorsal edge, with its two more or less developed, 

 terminal, horn-like angles, are well shown. In some instances 

 the depression consists of a single, shallow, roundish pit, just 

 above the centre of the valve, as in Primitia cristata, J. & IL, 

 Ann. Nat. Hist. ser. 3. vol. xvi. pi. 13. fig. 1 ; sometimes it is 

 lengthened longitudinally, as in P. umbilicata, J . & H., loc. cit. 

 fig. 2 ; and frequently this seems to divide into two more or 

 less distinct pits. Fig. 6 a shows the extreme condition of the 

 double pit, with a trace only of the longitudinal depression 

 between them. The many stages of variation observable in 



