84 Description of Entomostraca, &c. 



"Carapace-valves thin, nearly oblong, but somewhat higher 

 at the posterior third than anteriorly; umbo distinct, placed 

 forward, being situated at the antero-dorsal angle, beyond 

 which the convexity of the anterior border projects but 

 slightly ; posterior border boldly rounded, usually more or 

 less elliptical and oblique ; ventral border gently and ob- 

 liquely convex. The surface of the valves presents numerous 

 concentric wrinkles (30 — 50 or more), some of which appear 

 to be the raised ridges usual in Estlierice, and the others are 

 due to finer intermediate strise. The surface is frequently 

 found to be wrinkled transversely with very delicate corruga- 

 tions crossing the concentric ornament, and due to mechani- 

 cal causes. Coarser Avrinkles, also due to the crumpled state 

 of the fossil valves, are often seen in some of the Lammerton 

 specimens ; the latter seem to aifect the inner portion of the 

 shell, which sometimes shows a cellular appearance analogous 

 to the reticulate structure of crustacean shell. This reticular 

 tissue is found freely dispersed on the shale from Lammerton, 

 over some portions where but little other trace of the Esthe- 

 rian valve itself remains. Where the boundaries of the 

 meshes make strong lines parallel with the concentric lines 

 of growth of the shell, the fine intermediate stria3 of the 

 surface would probably be stronger than where the reticula- 

 tion is irregular. 



" Of B. striata I have seen numerous specimens from 

 several different localities ; namely, — 1. From Lammerton, 

 Berwickshire ; in bituminous shales belonging to the moun- 

 tain limestone series. 2. From the Lanarkshire coal field 

 (in cannel coal). 3. From Silesia, in carbonaceous shales 

 of the lower coal measures. 4. From two places in Lanca- 

 shire, in cannel coal of the middle coal m-easures, and in 

 bituminous shale of the lower coal measures. 5. From near 

 Chesterfield, Derbyshire, in carbonaceous shale of the lower 

 coal measures. 



*^ Differences of outline are to be observed among the vari- 

 ous individuals ; and some of these variations appear to be 

 limited to one or other of the groups of specimens from the 

 five localities mentioned. It is convenient, therefore, to seize 

 these distinctions, slight as they are, and certainly not of 

 specific value (nothing of the body and limbs of animals re- 

 maining to help our judgment), and make them serviceable 

 in the recognition of the several very similar forms of cara- 

 pace from widely separate places, and from at least four dis- 

 tinct horizons in the carboniferous group of strata. 



